5.1$surround$sound:$ the!digital!audio!multichannel!format ...€¦ ·...

The Brown Book, November 2008

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5.1 surround sound: the digital audio multichannel format developed by the Moving Picture Experts Group (see: MPEG) for digital soundtrack encoding for film, laserdiscs, videotapes, DVD, and HDTV broadcast. The designation "5.1" (first proposed by Tom Holman of THX fame) refers to the five discrete, full bandwidth (20-20kHz) channels - left, right, & center fronts, plus left & right surrounds - and the ".1" usually refers to the limited bandwidth (20-120Hz) subwoofer channel, but can also refer to a special effects/feature channel. Terminology used by both Dolby Digital and DTS Consumer (the home version of their theater Coherent Acoustics system). A-B'ing: comparing two programs by frequently switching back and forth between them. acoustics: the study of the physics of sound. ADAT (Alesis Digital Audio Tape): Digital tape recording system developed by Alesis, and since licensed to Fostex & Panasonic, putting 8-tracks of 16-bit, 44.1kHz digital audio on S-VHS tape. ADAT Optical: Alesis's proprietary multichannel optical (fiber optic) digital interface specification for their family of ADAT modular digital multitrack recorders. This standard describes transmission of 8-channels of digital audio data through a single fiber optic cable. additive synthesis: a synthesis technique that is based on the combining of simple waveforms (usually sine wave) at various frequencies, amplitudes and phases to create a more complex waveform. ADSR: the abbreviation for the classic four stage envelope: Attack, Decay, Sustain, Release. AES (Audio Engineering Society): Founded in 1948, the largest professional organization for electronic engineers and all others actively involved in audio engineering. Primarily concerned with education and standardization. AES3 interface (The interface formerly known as AES/EBU. Use of AES3 interface clarifies that the interface includes the isolation required by AES3 but not required by the EBU specification.) The serial transmission format standardized for professional digital audio signals (AES3-1992 AES Recommended Practice for Digital Audio Engineering - Serial Transmission Format for Two-Channel Linearly Represented Digital Audio Data) A specification using time division multiplex for data, and balanced line drivers to transmit two channels of digital audio data on a single twisted-pair cable using 3-pin (XLR) connectors. Issued as ANSI S4.40-1985 by the American National Standards Institute. In addition, information document AES-3id is available describing the transmission of AES3 formatted data by unbalanced coaxial cable. Transmission by fiber optic cable is under discussion. The consumer version is referred to as S/PDIF.


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Aftertouch message: a type of three-byte MIDI command that sends information on a specified channel about how pressure was applied to a key after it was played. Aftertouch may be used as a time-variant controller. AIFF: acronym for Audio Interchange File Format, the standard audio format for audio files on the Apple Macintosh platform. algorithm: a step-by-step procedure for accomplishing a task. Each step must be unambiguously defined resulting in a clear path to the resolution of a problem to be solved. aliasing: aliasing is the term used to describe the unwanted frequencies which are produced when a sound is sampled at a rate which is less than twice the frequency of the highest frequency component in the sound. ambience: the portion of the background sound in a music hall, auditorium or listening environment other than that resulting from reflected program sound. Ambience includes intrusion of natural environmental noise inherent in the location, air-conditioning noise, audience noise, etc. amplifier: a modifier module in the synthesis process which controls than amplitude of a signal. amplitude modulation: change induced in the amplitude of a signal by means of a control signal of a time-variant controller. Also called AM. amplitude: refers loosely to the strength of the waveform in terms of the amount of fluctuation between the peak positive value or the peak negative value and the zero axis, or to a single instantaneous value at any point of the waveform. The amplitude of a sound contributes greatly to the perceived volume. analog recording: a way of documenting the fluctuating voltages of an analog signal over time by imprinting a magnetic record on recording tape whose magnetic imprint is analogous to fluctuations in the voltage that it records. analog signal: an electrical signal that represents sound by containing voltages that fluctuate analogously to the fluctuations contained in the air pressure. analog synthesizer: an instrument that produce analog representations of sound, which the user may design. Presumably these "synthesized" sounds will be subsequently converted to acoustic energy so that we may hear them. analog to digital converter (A/D converter, also ADC): a device which changes an analog signal to a digital representation of sound. This digital representation is a series of numbers that represents the fluctuating voltage of the analog signal.


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anechoic: literally, without echo, used to describe specially designed rooms, anechoic chambers, built to emulate a free sound field, by absorbing practically all the sound field. ANSI (pronounced "ann-see", American National Standards Institute): a private organization that develops and publishes standards for voluntary use in the U.S.A. array: a set of values stored sequentially in computer memory. ASCII (pronounced "ask-ee", American Standard Code for Information Interchange): an ANSI standard data transmission code consisting of seven information bits, used to code 128 letters, numbers, and special characters. ASIO (audio stream input/output): a multichannel audio transfer protocol developed by Steinberg North America in 1997, for audio/MIDI sequencing applications, allowing access to the multichannel capabilities of sound cards. attack: the first stage of an envelope, but may have other meanings depending on context. attenuate: to reduce in amplitude. axial modes: acoustical resonance effects between two spaced, parallel surfaces, such as side walls of a room, end walls and floor/ceiling. balanced line: a circuit in which two branches are electrically alike and symmetrical with respect to a common reference point, usually ground." This is the essence of a balanced interconnect. Namely, that two lines are driven equally and oppositely with respect to ground. band-pass filter: a modifier module in the synthesis process which permits frequencies within a specified bandwidth to pass and removes or attenuates frequencies outside of this bandwidth. band-reject filter: a modifier module in the synthesis process which removes or attenuates frequencies within a specified bandwidth and permits frequencies outside of this bandwidth to pass unaltered. bandwidth: the band of frequencies comprised of all frequencies between a defined upper frequency and a defined lower frequency. basic synthesizer: a simple configuration of the oscillator, filter and amplifier modules. BeOS (Be operating system): an operating system (OS) developed by Be Incorporated in 1996, called the first true "media OS," it is becoming very popular for Internet appliances, as well as software designed for live performance venues.


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bit: one of the two values 0 or 1 that is used in the binary number system. boot: starting up a computer by loading a program that allows it to run other programs. The term comes from bootstrapping which means that the computer "pulls itself up by its own bootstraps." bounce: when recording or sequencing, to bounce tracks means to combine (mix) several tracks together and record them on another track. buffer: an area of computer memory that is used to temporarily store data. bug: an error in a computer program that causes it to work incorrectly. byte: a computer word made up of eight bits of data. cancellation: the attenuation that occurs when two identical signals of opposite polarity occur. cardioid: a directional microphone with a heart shaped, narrow pattern, which picks up from directly in front of the mic. carrier wave: the wave to which modulation is applied. The carrier wave is altered in sympathy with the modulating signal. CD (compact disc): trademark term for the Sony-Philips digital audio optical disc storage system. The system stores 75 minutes (maximum) of digital audio and subcode information, or other non-audio data, on a 12-centimeter diameter optical disc. The disc is made of plastic, with a top metallized layer, and is read by reflected laser light. Variations (such as the 3" disc) are reserved for special applications. center frequency: the frequency around which the passband of a filter is symmetrically disposed. central processing unit (CPU): a microprocessor or computer which is used to perform complex task-related functions. Within an electronic musical instrument, it is a dedicated computer system for handling the many performance and control-related messages and commands that must be processed in real time. cents: 1/100th of a semi-tone chip: an integrated circuit. chorus: a voice doubling effect created by layering two identical sounds with a slight delay (20-50 ms) and slightly modulating the frequency of one or both of the sounds.


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clock: in reference to a MIDI sequencer small, equally spaced time-divisions of a quarter note. close miking: a microphone placement technique which involves placing a microphone close to the sound source in order to pick up mainly direct sound, and avoid picking up reverberant sound. codec (code-decode also compression-decompression): originally a device for converting voice signals from analog to digital for use in digital transmission schemes, normally telephone based, and then converting them back again. Broaden now to mean an electronic device that converts analog signals, such as video and voice signals, into digital form and compresses them to conserve bandwidth. Most codecs employ proprietary coding algorithms for data compression, common examples being Dolby's AC-2, ADPCM, and MPEG schemes. It is data compression (and direct digital video & audio inputs) that has evolved the newer meaning of compression-decompression. combiner: a synthesis module that combines the audio signals from several or many sources. Often a combiner is given a formal name within a system, and many times the combining function occurs transparently without the user having to include it in the synthesis process. Also called a mixer. complex waveform: any waveform comprised of multiple frequencies. compression ratio: in a compressor, the ratio of dB change in input level to the dB change in output level. compressor: an amplifier whose gain decreases as its level is increased. computer music: used in reference to a variety of musics that are composed with the use of the computer. In some cases the actual sound production arises from the computer itself, and in other cases the computer is functioning as control unit. condenser mic: a microphone which converts sound pressure level variations into variations in capacitance and then into electrical voltage. Console: a term for a sound mixer, usually a large desk-like mixer. constructive interference: when the amplitude of one wave or frequency combines with the amplitude of one or more waves or frequencies to create an increase in amplitude. control change message: a type of three-byte MIDI command that sends information on a specified channel about how a particular musical parameter on the corresponding channel should changed over the course of time. control signal: the signal output by a time-variant controller.


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cosine wave: a sinusoidal waveform whose phase relative to the sine wave is 90 degrees. crossfade: to gradually fade out one sound while fading in another so that a seamless transition is made between the two sounds. crosstalk (signal): 1. undesired capacitive, inductive, or conductive coupling from one circuit, part of a circuit, or channel, to another. 2. any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. cutoff frequency, fc: the specific frequency above which, or below which, (depending on the filter type) frequencies are removed or attenuated. cycle: a single, complete occurrence of a waveform pattern. cycles per second (c.p.s.): how frequency is expressed, the same as Hertz. DA-88: Tascam's model number for their digital multitrack recorder using Sony-developed "Hi8" 8 mm videotape as the storage medium. Becoming a generic term describing this family of recorders. Newer versions include the DA-78 and DA-98. daisy chain: a type of configuration for a MIDI system where MIDI data is transmitted from one instrument to the next, to the next, and so on. DAT (digital audio tape recorder ): a digital audio recorder utilizing a magnetic tape cassette system with rotary heads similar to that of a video recorder. data byte: one of two types of bytes in the MIDI protocol. Data bytes have numerical values ranging from 0 to 127 and specify additional information about what is to be done and often come in pairs. Data bytes are always preceded by a status byte and are identifiable because their first bit is always "0". data: information a computer needs in order to make decisions or carry out a particular action. DAW (digital audio workstation): any of several software/hardware systems using a computer as the basis for creating, editing, storing, and playback of digital audio, using the computer's hard disk as the recording medium. dead: description of a sound in which reverberant information is severely attenuated or completely missing. decay: the second stage of a four stage envelope, but may have other meanings depending on context.


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decibel (dB): a reference for the measurement of sound energy. The minimum change in volume that the human ear can perceive. Named after Alexander Graham Bell. A decibel is 1/10th of a Bel;; a unit of relative measure used to compare the intensities of two signals on a logarithmic scale. Under certain conditions the decibel can be used to compare the amplitudes of two signals as well. destructive interference: when the amplitude of one wave or frequency combines with the amplitude of one or more waves or frequencies to create a decrease in amplitude. diaphragm: the moving membrane in a microphone or loudspeaker. dictionary: a malevolent literary device for cramping the growth of a language and making it hard and inelastic. This dictionary, however, is a most useful work. DSP: acronym for digital signal processing, which refers to manipulating analog information, such as sound or photographs that has been converted into a digital form. DSP also implies the use of a data compression technique. When used as a noun, DSP stands for digital signal processor, a special type of co-processor designed for performing the mathematics involved in DSP. Most DSPs are programmable, which means that they can be used for manipulating different types of information, including sound, images, and video. Digital Audio Tape (DAT): the medium that a machine that records sound digitally uses. They generally use a spinning drum similar to those found in VCR's as opposed to the record and playback heads found on regular analog tape recorders. digital audio: the use of sampling and quantization techniques to store or transmit audio information in binary form. The use of numbers (typically binary) to represent audio signals. digital recording, digital sample: a generator module in the synthesis process which outputs a sound that has been previously recorded. digital recording: a way of documenting the fluctuating voltages of an analog signal over time by taking measurements of the instantaneous amplitudes in the analog signal at equally spaced time intervals. The measurements of the amplitude are usually thousands of times per second with 44,100 times per second being a standard rate. digital sampling: the process of converting an analog representation of sound to a digital representation of sound by taking measurements of the instantaneous amplitudes at equally spaced time intervals. These measurements of the amplitude are usual taken thousands of times per second.


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digital synthesizer: an instrument that produce digital representations of sound, which the user may design. Presumably these "synthesized" sounds will be subsequently converted to an analog signal, and then to acoustic energy so that we may hear them. digital to analog converter (D/A converter, also DAC): a device which takes the series of stored numbers, the digital representation of sound, and changes it back to an analog signal. disk: a peripheral device for storing large quantities of information. For example a hard drive. distant miking: a microphone placement technique which involves placing a microphone far from the sound source in order to pick up a high proportion of reverberant sound. distortion: an unwanted change in a waveform as it passes through an electronic or software component, or from one medium to another. dither: the noise (analog or digital) added to a signal prior to quantization (or word length reduction) which reduces the distortion and noise modulation resulting from the quantization process. Although there is a slight increase in the noise level, spectrally shaped dither can minimize the apparent increase. The noise is less objectionable than the distortion, and allows low-level signals to be heard more clearly. DOS (disk operating system, pronounced "doss") : a software program controlling data in memory, disk storage, running programs and I/O management. dry recording: the practice of recording a signal without applying artificial reverberation. dry sound: a description of a sound that lacks reverberant information. duty cycle: in describing square and rectangle waves, the percentage of the waveform that occurs above the zero axis. A square wave always has a 50% duty cycle, rectangle waves have a duty cycle other than 50%. DVD: (Officially "DVD" does not stand for anything. It used to mean "digital versatile disc" - and before that it meant "digital video disc" also known as hdCD in Europe.) A 12-centimeter (4.72") compact disc (same size as audio CDs and CD-ROMs) that holds 10 times the information. Capable of holding full-length movies and a video game based on the movie, or a movie and its soundtrack, or two versions of the same movie - all in sophisticated discrete digital audio surround sound. The DVD standard specifies a laminated single-sided, single-layer disc holding 4.7 gigabytes, and 133 minutes of MPEG-2 compressed video and audio. It is backwards compatible, and expandable to two-layers holding 8.5


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gigabytes. Ultimately two discs could be bounded together yielding two-sides, each with two-layers, for a total of 17 gigabytes. There are four main versions: DVD-Video (movies) as outlined above;; DVD-Audio (music-only): the standard is flexible, allowing for many possibilities, leaving the DVD-player to detect which system should be used. Choices include 74 minutes for 2-chs at 24-bits, 192 kHz sampling, or 6-chs at 24-bits, 96 kHz, all utilizing lossless compression (type MLP for Meridian Lossless Packing). Quantization can be 16-, 20-, & 24-bits, with sampling frequencies of 44.1, 88.2, and 176.4 kHz, as well as 48, 96, and 192 kHz all supported. DVD-ROM (read-only, i.e., games and computer use). DVD-RAM (rewritable, i.e., recording systems). Matsushita is currently the leader in density with 4.7Gb and 9.4Gb claimed for single-sided and double-sided discs respectively, compared with 2.6Gb and 5.2Gb offered by standard DVD-RAM technology. dynamic mic: a microphone in which the diaphragm moves a coil suspended in a magnetic field in order to generate an output voltage proportional to the sound pressure level. dynamic range: in musical instruments, a measure in the span between the quietest and loudest sounds it is capable of producing. In a tape recorder, the dB interval between the systemic noise level and the level at which 3% distortion occurs. EBU (European Broadcasting Union): an international professional society that, among other things, helps establish audio standards. electroacoustic transducer (transducer): a transducer is a device that converts one type of energy to another type of energy. electronic music: used in reference to a variety of musics that are composed with the use of any electronic instrument or device that are played back through loudspeakers. At least as often the word "electro-acoustic music" is used in the same way. In some instances, electronic music is used to describe a particular class of "electro-acoustic music" that does not use any prerecorded or sampled material. envelope generator: a time-variant controller that outputs a non-periodic, time-variant control signal which induces changes in other synthesis modules. The shape of the control signal it outputs is called the envelope, and can be defined by specifying times and levels in each of the envelope stages. envelope: the non-periodic, time-variant shape output by an envelope generator.


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equalization: any intentional modification of the audio spectrum. equalizer: a device which attenuates or boosts of selected frequencies in the audio spectrum. Equalizers usually contain many bands to allow the user a fine degree of frequency control over the sound. expander: an amplifier whose gain decreases as its input level is decreased. feedback: the return of some portion of an output signal to the system's input. FFT (Fast Fourier Transform): a numerical technique for determining the spectrum of a digital sound. filter modulation: change induced in the frequency of the cut-off frequency of a filter by means of a control signal of a time-variant controller. filter: a modifier module in the synthesis process which allows certain specified frequencies that are sent into it to pass through it unaltered, and at the same time removes or attenuates other frequencies specified frequencies. FireWire: a popular name for a high-speed digital standard capable of transferring data at up to 800 Mb/sec. Firewire connections are used for connecting peripherals such as digital video cameras, audio components and computer devices. FireWire was originally developed by Apple Computer as a replacement for the SCSI bus. IEEE 1394 is formal name for the standard. Vendors must obtain a license from Apple to use the term FireWire. flange: an effect created by layering two identical sounds with a slight delay (1- 20 mS) and slightly modulating the delay of one or both of the sounds. The term comes from the early days of tape recording when delay effects were created by grabbing the flanges of the tape reels to change the tape speed. Fletcher-Munson Curves: same as equal loudness curves. FM synthesis: the alteration or distortion of the frequency of one oscillator by a signal from a modulating oscillator. This produces a waveform with many more spectral components than the presence of only two oscillators might seem to imply. Foley: a term synonymous with film sound effects. A recording studio Foley stage is where the sound effects are generated in sync with the moving picture. Named after Jack Foley, who invented sound effects for film sound while working for Universal. He simultaneously added music and effects to the previously silent film "Showboat" and the first "Foley" session was born. Fourier Analysis: a method of analysis that breaks complex waveforms into its component frequencies.


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Fourier Synthesis: the building of a complex periodic waveform by combining sine waves of various frequency, amplitude and phase. frequency modulation: change induced in the frequency of a signal by means of a control signal of a time-variant controller. Also called FM. frequency: the rate at which one cycle of a waveform is completed;; frequency is expressed in cycles per second c.p.s. or Hertz, Hz. fundamental frequency, fundamental: the frequency that has the same period as the waveform. The fundamental frequency will always be the lowest frequency in a waveform. gain: in a device (or software object), the ratio of output amplitude to input amplitude. When gain is larger than one, amplification exists. gain riding: manually the gain in a signal path in an effort to decrease the dynamic range. generator: a general classification of synthesis modules. A generator is a module that initially generates the sound material which will subsequently be modified. Examples include the oscillator, the noise generator, and the digital recording. ground loop: hum caused by currents circulating through the ground side of a piece of equipment or system. This is due to grounding it at points of different voltage potential. hard disk recorder: a computer-based hardware and software package specifically intended for the recording, manipulation, and reproduction of the digital audio data that resides upon hard disk and/or within the computers own RAM. hard disk: a storage medium for digital data which can hold more information and access it faster than a floppy disk. hardware: the electronic equipment that forms a computer system. harmonic series: the relationship between the fundamental frequency and the upper partial frequencies when the partials are whole number multiples of the fundamental frequency. harmonic spectrum, spectrum: describes the specific harmonic makeup and the specific amplitude of each harmonic frequency contained in a waveform. A spectrum may also be inharmonic.


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harmonics: partial’s frequencies that multiples of the fundamental frequency, e.g., 200, 300, 400, 500, and 600 Hz are harmonics of the fundamental frequency 100 Hz. The fundamental is the first harmonic. Hertz , Hz: how frequency is expressed, the same as cycles per second. high-pass filter: a modifier module in the synthesis process which permits frequencies higher than a specified frequency (fc) to pass and removes or attenuates frequencies lower than this frequency. HTML (hypertext markup language): the software language used on the Internet's World Wide Web (WWW). Used primarily to create home pages containing hypertext. interleaving: an error concealment scheme (in digital audio), in which sequential data words are first separated and then recorded in odd and even groups (e.g., 1, 3, 5, 7, 9, 11, 2, 4, 6, 8, 10, 12). I/O (Input/Output): a class of devices that provide the means for communication between the computer and its users or other computer hardware. input: to send a signal into a synthesis module or other device. The signal may be an analog or digital audio signal, or it may be MIDI data. interactive: characteristic of a situation where the user and the computer program respond to each other's actions on an approximately real-time basis. Any live-performance situation is, by definition interactive. interface: the boundary or means of connection between two or more elements in a computer system. An interface can be between hardware devices, pieces of software, or a user and a computer system. interpolation: the process of finding values intermediate to specified values. The two most common methods of interpolation are linear and exponential. Java: the trademarked name for a powerful object-oriented programming language developed by Sun Microsystems. Java allows high-speed fully interactive Web pages to be developed for the Internet or any type of platform. jitter: a tendency towards lack of synchronization caused by electrical changes. Technically the unexpected (and unwanted) phase shift of digital pulses over a transmission medium. A discrepancy between when a digital edge transition is supposed to occur and when it actually does occur - think of it as nervous digital, or maybe a digital analogy to wow and flutter. keyboard controller: a MIDI-controller with a piano-like keyboard that is "played" and that sends MIDI information out to other instruments in the system.


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kHz (kilohertz): one thousand (1,000) cycles per second. kilohertz: equal to 1000 Hertz. LAN (local area network): a combination of at least two computers and peripherals on a common wiring scheme, which allows two-way communication of data between any devices on the network. Law of the First Wavefront: the first sound to strike the ears determines the perception of direction. LCD (liquid crystal display): a display of numerical or graphical information made of material whose reflectance or transmittance changes when an electric field is applied. An LCD requires ambient light or back-lighting for viewing. LED (light emitting diode): a self-lighting semiconductor display of numerical or graphical information based on the light emitting characteristics of a solid-state device that emits incoherent (i.e., random direction) light when conducting a forward current line-level: standard +4 dBu or -10 dBV for analog audio signals that describes the nominal level.. Linux: a computer Unix-type operating system (OS) invented by Linus Torvalds in 1992, who wrote it as a student at the University of Helsinki. He created this OS because he couldn't afford one that could accomplish what he wanted with his available hardware. He then posted it on the network for other students, where it grew and became very stable and powerful. Today, for free, the software, source code, etc., is available off the web. localization: the process of synthesizing cues that create the auditory illusion of the placement in space of a sound source. looping: when, in digital sampling, a portion of the digital recording is directed to play repeatedly. loudness: the subjective response to the amount of acoustical power received by the ear. loudspeaker: a transducer that converts an analog signal back into acoustic energy that we can hear;; usually loudspeakers come in pairs to produce a stereophonic effect, however, sometimes a cluster containing many speakers are used. low-frequency oscillator, LFO: is a time-variant controller which by outputting frequencies in the subaudio range can induce change in a generator, a filter, or an amplifier depending on which module is the destination of an LFO control signal.


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low-pass filter: a modifier module in the synthesis process which permits frequencies lower than a specified frequency (fc) to pass and removes or attenuates frequencies higher than this frequency. Markov process: a conditional random process in which the higher-order probabilities can be calculated as products of first order probabilities. Mastering: a process whereby a number of songs, after being mixed down, are EQ'd, compressed as necessary, and balanced in volume with each other, so that they will sound good when placed together on a CD. MDM (modular digital multitrack): generic term used to describe any of the families of digital audio multitrack recorders. The most common examples being the Alesis ADAT series and the Tascam DA-88 series. mic-level: nominal signal coming directly from a microphone. Very low, in the microvolts, and requires a preamp with at least 60 dB gain before using with any line-level equipment. microphone: a device that converts waves of acoustic energy to electrical energy;; sometimes called an electroacoustic transducer , or transducer for short. microphone preamplifier: the first stage of amplification which raises microphone levels to line levels. microprocessor: an integrated circuit that performs a variety of operations in accordance with a list of instructions. The core of a microcomputer or personal computer, a one chip computer. MIDI cable: a specific type of cable with a 5-pin plug at each end through which MIDI data is transmitted from one instrument to another. MIDI channel: a numerical designation from 1-16 associated with MIDI messages and instruments contained in a MIDI system. MIDI IN port: MIDI port through which MIDI data is received. Information may not be received through any other port. MIDI interface: a device that assists and permits the flow of MIDI data to and from the computer to and from instruments in the MIDI system. MIDI mode: describes how a module will respond to incoming MIDI data. MIDI OUT port: MIDI port out of which MIDI messages are transmitted, if and only if, the information originates in that instrument.


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MIDI sequencer: a hardware device that is programmed specifically to record, edit and play back MIDI data or a software program resident in a computer that carries out these same tasks. MIDI THRU port: port which outputs a replica of any MIDI data that is received at the MIDI IN port. This replica is output virtually at the instant it is received. MIDI, Musical Instrument Digital Interface: a protocol that allows messages to be sent as digital data from one musical instrument to other musical instruments or computers. MIDI controller: an instrument that is "played" and that sends MIDI information out to other instruments in the system. Instruments with the piano-like keyboard are the most common. millisecond (msec): one one-thousandth (.001) of a second. mixer: a synthesis module that combines the audio signals from several or many sources. Often a combiner is given a formal name within a system, and many times the combining function occurs transparently without the user having to include it in the synthesis process. Also called a combiner. The term mixer is also used to describe a hardware device that combines signals from multiple sources. Non-software mixer come in many sizes and are referred to by the number of channels (different audio inputs) they have. modifier: a general classification of synthesis modules. A modifier is a module that changes the sound material sent to it. Examples include a filter and amplifier. modulation: to induce change in a synthesis module by means of a control signal that varies over time. At one time the use of the term modulation was limited to those changes which were periodic, like those that might be induced by an LFO;; however, current usage also includes changes induced by time-variant controllers that output non-periodic control signals. monitor: this word can mean at least two different things: a computer screen or a studio or stage speaker system. Mono mode, Omni Off, Mono: MIDI mode where an instrument is enabled to respond to only one note at a time and only on the single channel on which the message is transmitted. Also called Mode 4. MP3 (MPEG-1, layer 3): a type of digital audio compression popularized for transmitting songs over the Internet. MP3 allows real-time audio streaming for Internet encoding and downloading. MP3 files are identified by the suffix ".MP3" Typically MP3 compresses CD-quality audio down to about one minute per 1MB file size.


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MS-DOS (Microsoft disk operating system): Microsoft's registered trademark for their PC operating system. MSB (most significant bit): the bit within a digital word that represents the biggest possible single-bit coded value. Multi-mode: MIDI mode where an instrument is enabled to respond like multiple sound producing instruments on multiple channels and with multiple "synthesized" sounds. multi-track: a way to record a complex musical piece by dividing it into simple tracks and combining the tracks during playback. musique concrete: a form of tape or electronic music made from "concrete" i.e. recorded sounds. In most music concrete the recorded sounds are modified electronically from their original form. near-field monitor: a loudspeaker used at a distance of 3-4 feet in recording studios. nibble: a group of four bits or half a byte (8-bits). noise generator: a generator module in the synthesis process which outputs noise. noise: a "hissing" type of sound containing the random occurrence of all frequencies within the audible range. non-periodic waveform: a signal that is not made up of repetitions of the same wave form. normalize: a digital processing function that increases the amplitude of a sound file until the peak amplitude of its loudest sample reaches 100% of full scale. Note Off message: a type of three-byte MIDI command that stops a note from playing on a specified channel. Note On message: a type of three-byte MIDI command that plays a note on a specified channel. Nyquist frequency: the highest frequency a given sample rate can accurately represent. Nyquist rate: a sampling rate two times the highest frequency contained in a waveform. Object-oriented or object-based programming (Abbreviated OOP): a software technique in which a system program is expressed completely in terms


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of predefined things (objects), consisting of a set of variables and operations which can be performed on them, and the connections between objects. octave: the interval between any two frequencies that are in a 2:1 ratio. off-axis: not directly in front of a microphone or speaker. on-axis: directly in front of a microphone or speaker. Omni mode, Omni On, Poly: MIDI mode where an instrument is enabled to respond to one note or more than one note at a time without discriminating the channel on which the message is transmitted. Also called Mode 1. operating system (OS): an organized collection of software which provides many useful services to the users of a computer. It also controls the flow of work in the system. oscillator: a generator module in the synthesis process which outputs periodic waveforms at frequencies that can be specified. out of phase: describes the temporal relationship of two or more waves. output: to send a signal out of a synthesis module or other device. The signal may be an analog or digital audio signal, or it may be MIDI data. overtone: an overtone is any harmonic other than the fundamental. The first overtone is the second harmonic. pan: refers to the placement or moving of an audio signal left or right in the stereo field. partials: frequencies in a waveform that are higher than the fundamental. The frequencies may be harmonic or inharmonic. period: the time-span occupied by one complete cycle of a waveform. periodic waveform: a type of waveform whose pattern of fluctuation continuously repeats. phantom power: the term given to the standardized scheme of providing power supply voltage to certain microphones using the same two lines as the balanced audio path. phase: used to specify a particular point in time on the waveform, or to compare the relative position in time of two waveforms. The phase is described in terms of degrees from 0 to 360 degrees, 90, 180, and 270 marking the 1/4, 1/2, and 3/4 points, respectively.


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pink noise: a common type of noise which has equal amplitudal distribution of all frequencies between any octave. Pitch bend message: a type of two-byte MIDI command that sends information on a specified channel about how the pitch of a note or notes on the corresponding channel should changed over the course of time. pitch: the subjective response to a frequency. Poly mode, Omni Off, Poly: MIDI mode where an instrument is enabled to respond to one note or more than one note at a time and only on the single channel on which the message is transmitted. potentiometer: a variable resistor with three terminals;; the two ends of the resistor and a slider or knob. A potentiometer is often used to control an electronic circuit by reporting changes in resistance and is often found audio devises such as mixers to control levels. Proximity Effect: when cartioid microphones are placed very close to the sound source, a boosting of the bass frequencies occurs which is known as the proximity effect. psychoacoustics: the study of the way humans perceive sound. It includes such subjective responses to sound as pitch, loudness, duration, timbre, and apparent location. pulse wave: a waveform where the harmonics spectrum is dependent on its duty cycle in that the only harmonics that are missing correspond to the duty cycle. If the duty cycle is 1/3, then every third harmonic is missing (3, 6, 9, etc.), if the duty cycle is 1/4, then every fourth harmonic is missing, and so on. The relative amplitude of the harmonics are expressed by the ratio 1/harmonic number. Also called a rectangle wave. Q: a measure of the selectivity of a filter. A filter with a high Q has a narrow bandwidth. quantization: the process of converting an infinitely-variable waveform into a finite series of discrete levels. RAM: acronym for Random Access Memory. The memory in a computer in a computer that stores data temporarily while you are working on it. Data stored in RAM is lost forever when power is interrupted to the machine if it has not been saved to another medium, such as floppy or hard disk. rarefaction: the instantaneous spreading apart of air particles during the negative going half cycle of a sound wave. The opposite of condensation.


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RCA (aka phono jack or pin jack): the Radio Corporation of America (RCA) originally developed this type of unbalanced pin connector for internal chassis connections in radios and televisions during the '30s. It became popular for use in the cables that connected phonograph cartridges to preamplifiers because it was inexpensive and easily fitted to the rather small diameter shielded cables used for the cartridge leads (then they were mono cartridges so single conductor shielded cables were adequate -- now you know). The standard connector used in line-level consumer and project studio sound equipment, and most recently to interconnect composite video signals. rectangle wave: a waveform where the harmonics spectrum is dependent on its duty cycle in that the only harmonics that are missing correspond to the duty cycle. If the duty cycle is 1/3, then every third harmonic is missing (3, 6, 9, etc.), if the duty cycle is 1/4, then every fourth harmonic is missing, and so on. The relative amplitude of the harmonics are expressed by the ratio 1/harmonic number. Also called a pulse wave. regeneration, resonance, emphasis: a parameter available on many filters which permits the frequencies at and around the cut-off frequency to be given greater prominence. release: the final stage of an envelope, but may have other meanings depending on context. resolution: the number of discrete amplitudes a digital recording or digital synthesis system can represent;; resolution is expressed in term of the number of binary digits (bits) used to represent each amplitudal value. 8-bit (256 values) or 16-bit (65, 536 values) are very common. response curve: a graphic depiction of how a filter, synthesis module, or other electronic device responds to a signal input to it. reverberation: the multiple reflections of sound in a room causing sound to be heard after all sources have ceased. ring modulation: the process of combining two signals by multiplication. Ring modulation produces sidebands but suppresses both the carrier and modulating frequencies. ROM: acronym for Read Only Memory. This is computer memory which can't be changed or erased. It is 'burned' into the computer or device. Most synthesizers have some sounds which are in ROM memory and can't be altered. S/PDIF (Sony/Philips Digital Interface Format, also seen w/o slash as SPDIF): a consumer version of the AES3 (old AES/EBU) digital audio interconnection standard based on coaxial cable and RCA connectors.


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sample: each individual measurements of the instantaneous amplitudes of an analog representation of sound. These measurements of the amplitude are usual taken thousands of times per second. sampling increment: in a digital oscillator, the amount added to the current phase to determine which location in the wave table to use next. The sampling increment is directly proportional to frequency. sampling rate: the rate at which measurements of the amplitude usually expressed in terms of number of samples taken per second. Sample rates of 44,100 per second between 192,000 per second are the most common. sawtooth wave: a waveform that consists of all of the harmonics, whose relative amplitudes are expressed by the ratio 1/harmonic number and whose even-number harmonics are 180 degrees out of phase. sequence: a musical document that a MIDI sequencer records, edits and plays back that reflects a list of MIDI events. serial: a type of transmission where bits of data are transmitted one at a time in a series. Serial transmission is used by the MIDI protocol. sideband: a product of modulation in which new frequencies are generated on either side (i.e., above and below in frequency) of a given frequency. signal to noise ratio (S/N): In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise. The higher the ratio, the less obtrusive the background noise is. sine wave (sinusoid): the single waveform with only one frequency. slope: refers to the acuteness or steepness of how a filter attenuates frequencies above (in the case of a low-pass filter) or below (in the case of a high-pass filter) the cut-off frequency. SMPTE (pronounced "simty", Society of Motion Picture and Television Engineers): acronym for Society of Motion Picture and Television Engineers who adopted a standard time code in order to synchronize video and audio. SMPTE information is in the form of Hours, Minutes, Seconds, and Frames. There are two types of SMPTE timecode, Longitudinal Time Code which can be recorded on audio tape, and Vertical Interval Time Code which is recorded on video tape. sound source: the object or thing that vibrates and causes the displacement of air molecules which we ultimately hear as sound.


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sound: the perception of fluctuations of air pressure;; we often divide sound into two parts: that which is objective, quantifiable and adheres to physical laws, and that which is subjective is psycho-acoustic. square wave: a waveform that consists only of odd-numbered harmonics, whose relative amplitude are expressed by the ratio 1/harmonic number, and whose harmonics are all in phase. stage: refers to one of the two more the segments of an envelope. Attack, decay, sustain, and release are the names of the stages of the common four stage envelope. status byte: one of two types of bytes in the MIDI protocol. Status bytes have numerical values ranging from 128 to 255 and commonly specify what is to be done, and often on what channel it is to be done. A status byte is always the first byte in a MIDI message and is identifiable because its first bit is always "1". subaudio: refers to frequencies that are lower than humans can hear, approximately 20 Hz. subtractive synthesis: a synthesis technique that is based on the removal or attenuation of specified frequencies by a filter. sustain: the third stage of a four stage envelope, but may have other meanings depending on context. synthesis: refers to the designing of analog or digital representations of sound that ultimately are "output" by a synthesis instrument. There are a variety of synthesis techniques among which are additive synthesis (the combining of sine waves at multiple frequencies, amplitudes and phases), subtractive synthesis (the use of filtering techniques to remove specified frequencies of a complex frequency spectrum), or FM synthesis (the modulation of the frequency of one signal by the frequency of a second signal thereby generating frequencies). sweet spot: the position giving the optimum listening conditions in a stereo reproduction environment;; often considered to be at a point forming an equilateral triangle with the two loudspeakers. synthesizer: an instrument that produce an analog or digital representations of sound, which the user may design. Presumably these "synthesized" sounds will be subsequently converted to acoustic energy so that we may hear them. TDIF (Tascam Digital Interface Format): Tascam's (Teac) 8-channel digital audio interface to their DA-88 digital multitrack recorder, using unbalanced signal transmission and a DB-25 type connector. threshold (with respect to compression): the level above which a compressor begins to function.


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time and level: two values that provide the means by which each stage of an envelope is specified. The "time" value specifies the duration it take to move from its current level to the next level that is specified. The "level" value specifies the level achieved during the specified time. time-variant control: to induce change in a generator or modifier module by means of a signal that varies over time. The changes induced by time-variant control will depend on what has been selected to be the destination of the control signal. time-variant controller: a module in the synthesis process which outputs a control signal that induces change analogous to the shape it outputs. TOSLINK (Toshiba link): a popular consumer equipment fiber optic interface based upon the S/PDIF protocol, using an implementation first developed by Toshiba. transport: in a tape recorder, the system of motors, tape guides, etc., used to move the tape past the head assembly. triangle wave: a waveform that consists of odd-numbered harmonics, whose relative amplitudes are expressed by the ratio 1/harmonic number squared, and whose every other harmonic is 180 degrees out of phase. TRS (tip-ring-sleeve): 1. "Stereo ?" connector consisting of tip (T), ring (R), and sleeve (S) sections, with T = left, R = right, and S = ground/shield. 2. Balanced interconnect with the positive & negative signal lines tied to T and R respectively and S acting as an overall shield. 3. Insert loop interconnect with T = send, R = return, and S = ground/shield. [Think: ring, right, return] tweeter: a high frequency loudspeaker. ultrasonic: refers to frequencies that are higher than humans can hear, approximately 20 kHz. unbalanced line: a cable that transmits the audio signal between one wire and ground. USB: (Universal Serial Bus) a high-speed peripheral standard capable of transferring data at up to 12 Mb/sec. USB is used for many audio and MIDI devices such as MIDI interfaces variable: in recent synthesis systems, a numerical value that is entered to specify some parameter. VCA (Voltage Controlled Amplifier): an electronic circuit comprised of three terminals: input, output and control. The output voltage is a function of the input


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voltage and the control port. The gain of the stage is determined by the control signal, which is usually a DC voltage, but could be a current signal or even a digital code. Usually found as the main element in dynamic controllers, such as compressors, expanders, limiters, and gates. VCF (Voltage Controlled Filter): a filter whose cutoff frequency or resonant frequency is determined by a control voltage. Volume Unit (VU): a unit of measurement related to the ear's subjective impression of program level or loudness. Walla Walla: a city of southeast Washington near the Oregon border south-southwest of Spokane. Founded in 1856 near the site of an army fort, it is a manufacturing center in an agricultural region famous for sweet yellow onions. In spite of its name, a quiet community. WAV: The format for storing sound in files developed jointly by Microsoft and IBM. Support for WAV files is built into Windows 95/98/2000 operating system. WAV sound files are stored in an uncompressed format and end with the .wav extension. WAV files saved with file compression take on the extension of the compression codec;; example .mp3 waveform memory: the location in a digital synthesis system where a single cycle of waveforms are stored. Oscillators in a digital system may access this memory, and by repeating this single cycle over and over, the oscillator is able to produce a continuously sounding waveform. waveform selection: control associated with oscillators that permits the user to define the waveform output within the limits of the system. waveform: a graphic depiction of sound which shows the fluctuation of air pressure, voltages, or digital values over time. wet recording: the practice of recording artificial reverberation along with the direct signal. wet sound: a description of a sound that contains a high proportion of reverberant information.. white noise: a common type of noise which has an equal amplitudal distribution of all frequencies between any equal bandwidths. XLR: 1. originally a registered trademark of ITT-Cannon. The original model number series for Cannon's 3-pin circular connectors - invented by them - now an industry generic term. 2. the standard connector for digital and analog balanced line interconnect between audio equipment.


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For information regarding the following people, places and things Electric Sound: The Past and Promise of Electronic Music by Joel Chadabe is recommended. People Jon Appleton Milton Babbitt Donald Buchla John Cage Thaddeus Cahill Wendy Carlos John Chowning Mario Davidovsky Charles Dodge Herbert Eimert Pierre Henry Alvin Lucier Otto Luening Maurice Martenot Max Mathews Robert Moog Pauline Oliveros Les Paul Steve Reich Carla Scaletti Pierre Schaeffer Karlheinz Stockhausen Morton Subotnick Leon Theremin Friedrich Trautwien Vladimir Ussachevsky Edgard Varèse Barry Vercoe Iannis Xenakis


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Centers and Corporations Avid Bell Laboratories CCRMA CERL CNMAT Columbia-Princeton Electronic Music Center ICMA IRCAM M.I.T. Media Lab SEAMUS STEIM Yamaha Instruments 4X Workstation Buchla Synthesizer Csound DX-7 Dynamophone Kyma Max/MSP/Jitter Moog Synthesizer Music N Ondes Martenot RCA Mark II Synthesizer Synclavier Telharmonium Theremin Traautonium UPIC Compositions Come Out Gesang der Junglinge HPSCHD Philomel Poeme Electronique Silver Apples of the Moon Switched on Bach Symphonie pou un homme seul Synchronism(s) The Wild Bull

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