james truscott - sound design 1 (mu316)

7/30/2019 James Truscott - Sound Design 1 (MU316)

1/8

Sound Design 1 (MU316) Coursework 1

Lecturer : Andy Farnell

mes Truscott, BSc Music Technology Year 1


2/8

1

My FM/Wavetable Synth.

James Truscott


3/8

2

The synthesizer uses 2 forms of

synthesis to produce its tones.

Wavetable synthesis and

Frequency Modulation or FM

synthesis.

The FM counterpart is

constructed using a [sin~] or

sign wave oscillator to generate atone. It determines what

frequency is being sent to it by

the message being sent into its

left inlet. In this case i am

drawing note values from my

MIDI keyboard using a

"[notein]" object. the note in

object has three outlets the left

one being the MIDI note

number the middle being the

velocity variable and the right

being the MIDI channel number.in this case i used the first outlet

and fed the midi number into a

[stripnote] to "strip" the note

off signal. This means that when

i play a note in using the midi

keyboard, my envelope does not

get triggered by the note off

value, which would create 2

sounds. One when you press the

note, and one when you released

it.Once i had my stripped midi

number I used [mtof] to

generate a frequency value from

the MIDI note numbers, and

sent it to the inlet of my first

oscillator (the carrier

frequency). This means that

depending on which MIDI note I

trigger the corresponding

frequency will be sent to the

oscillator. I then created anotheroscillator [sin~] to serve as the

mod frequency. The mod

frequency oscillator is connected

to the carrier frequency inlet and

thereby modulates the frequency

of the carrier oscillator. the mod

frequency is generated by

dividing the carrier frequency by

4 (or "[* 0.25]"). However this is

quite a crude way of making sure

the modulation frequency is

relative to the carrier.

I think i could have bettered the patch by

setting some other relatable values foreach frequency by having calculations

with bang messages. For example you

could do a quarter as it is presently and

have the addition of doing halves eighths

or sixteenth fractions of the carrier fre-

quency.

The modulation index is user deter-

mined. I have done this because it adds

timbre to the sound and i think users

would appreciate having free reign over

the tone they require. The Mod index is

the number that the modulation fre-

quency is multiplied by, to create the final

modulation frequency.

FM counterpart ADSR envelope

The ADSR envelope i used was inspi

by the one also included in the RC-

patches available here.

(https://github.com/danomatika/rc

hes/tree/ master/rc-patches).

I used the rc-adsr~ as a template for

ADSR envelope and changed the inte

face. The envelope takes values from

sliders that determine the shape of th

velope. (attack=0-100 , decay=0-100

sustain=0-100, and release=0-200) t

are values in milliseconds which tell

envelope the duration of each stage o

process and the delay between the tr

ing of the note and when each stage s

The patch also includes an amp whic

will come in handy for blending my t

oscillators later.

Once the FM counterpart is complete

sent into a multiply box to be brough

good level and then sent to the [dac~

to get the envelope to effect the soun

must be routed into this multiply box

This is because when working with enlopes we are working with automatio

amplitude. We are sending the multi

tion variable into the box to determin

how much the amplitude has to be at

ated and when. as the envelope open

amplitude multiplication variable go

and as the envelope closes the multip

tion variable decreases.

Now that the envelope is in the chain

the correct place it requires triggerin
https://github.com/danomatika/rc-patches/tree/https://github.com/danomatika/rc-patches/tree/https://github.com/danomatika/rc-patches/tree/https://github.com/danomatika/rc-patches/tree/


4/8

3

To trigger the envelope we must send a bang

message to its left inlet. This tells the enve-

lope to start working. As i want the envelope

to trigger as i play my notes in, i decided totake my bang signal from the [stripnote],

because at this point in the chain i have a

clean MIDI message with no note off sig-

nal so it will bang as soon as the note is regis-

tered. To do this all i did was wire a bang

from the left outlet of [stripnote] and into

the inlet of my ADSR envelope. Now when i

play a note on my keyboard and i have set

my envelope parameters, the signal being

produced by my frequency modulation sec-tion is sculpted to follow the envelope of the

ADSR.

As a bit of interfacing for the FM module i

began creating the canvas for my project

and made a [vslider] for the modulation

index so the user can play around with the

multiplier a little easier. I then arranged myfirst module with some frequency displays.

The Wavetable Oscillator.

The Wavetable counterpart of this synthesizer uses a wavetable

cillator design from "Rc-patches" called rc-wave~ which i found

here. -->

(https://github.com/danomatika/rc-patches/tree/master/rc-pa

es.)

It uses "mtof" to determine the frequency to oscillate at and a

[tabosc4~] to allow you to draw in your desired wave shape. i ha

chosen this form of synthesis as i think it allows a lot of creativit

when creating sounds and also makes each sound unique becaus

it is not possible to draw the same wave twice without sending th

wave parameters as a message to the "tabosc4~". The wavetable

also contains a message that stops it from playing notes if the

MIDI note value is 0 this means it can be played like an instru-

ment. it only requires one creation argument which is the size of

the table, which can be any size as long as its a multiple of 4 so thit stays in tune with the frequency it is oscillating at.

I added a clear table message and a bang for the GUI so people

start fresh with a blank table if they choose. In retrospect it wou

have also been good to find a way of saving and loading the para

ters of the wavetable for later use incase you found a particularly

sweet sounding wavetable doodle and wished to reuse it later.

I gave the Wavetable oscillator its own envelope so it could mov

independently from the FM modules envelope and create a wid

more varied texture for the overall sound. Like the FM module toscillator must be sent to a multiply box to manipulate the ampl

tude with the ADSR controlling the multiplication variable.
https://github.com/danomatika/rc-patches/tree/https://github.com/danomatika/rc-patches/tree/


5/8

4

Bandpass filter

The bandpass filter i used is the [bp~] object. it has

3 inlets. The left inlet takes the audio signals to be

processed . To this inlet i connected the output of

both the multiplication boxes that the oscillators and

envelopes are connected to. The second inlet takes the

frequency at which the peak of the band is in the filter

envelope. To this i connected a knob with a range of

100 Hz - 3000 Hz as this is the frequency range that i

thought sounded best being effected. Also the knob

itself allows the user to sweep through the frequency

range easily and more freely. The right inlet is the Q

variable which determines the size of the band that is

being passed. I used a knob to set this parameter size

so its easy for the user to adjust by hand.

Graphic Displays

To create a more controlled feeling GUI i decided to add a

few extras which i like to see in Synths that i use. the first

of which and an essential in my eyes, an output channelstrip display, in this case i am using a [VU] object.

Im using send and receive boxes to send the signal from

the output of the bandpass filter into an envelope to show

the change in amplitude over time and then subtracted 100

from the signal to scale it to the [VU].

[VU] Display

Wave Shape Display.

Another thing which i love to see in a synthesizer, is a nice view of the oscillating wave so i can see how my tinker-

ing is affecting the sound. So i could not call my synth complete without one. The way i went about this is as fol-

lows.

First i created an array called wave-display that is 1000 milliseconds long. I then took a bang signal from the

[stripnote] and fed it into a [metro] i set the metro to trigger

every 125 milliseconds. I then routed that into another bang and

sent that into my [tabwrite~] sending data to wave-display. I

then wired the output of my filter into a subtraction box where 0.5 is

subtracted from the signal to bring it down in the array. From there

it is then fed in to the inlet of [tabwrite~ wave-display] this means

that when the note is played the [tabwrite~ wave-display] samples

the waveform every 125 milliseconds and outputs the data visually

in the array. i found that 125 milliseconds is often enough to take a

sample to get a smooth representation of the wave. However if you

wanted more accuracy you could reduce the number of milliseconds

thus increasing the amount of samples per second are being processed.


6/8

5

Record functionFor the recording section i have used [writesf~] the vari-

able is the amount of channels in this case 2 as we are in

stereo. [writesf~] requires 3 messages an open mes-

sage a start message and a stop message. however i

had trouble getting the recorded files to end up in the cor-

rect directory so i added a little extra object which makes

life a lot easier in this situation.

MIDI Controlls

As i had a few fun parameters mapped to my final GUI fo

the user to get creative with i thought it would be good to

map the modulation index [Vslider], the Filter Fre-

quency and the Q size to midi controllers .

Each controller that i wanted to use is set by the [ctlin]

ject. If you just use [ctlin] without a number it will have

outlets the middle outlet tells you what number controlle

you are moving. i found this useful when working out wh

controllers i wanted to use. When i had decided which kn

on my controller i wanted to map to each parameter on th

synth i added the controller number to the [ctlin] objec

[ctlin 9]. This fixes [ctlin] on the controller number th

you want to use .

When it is set this way you only get 2 outlets. The left is the value of the control 1-127 and the right the MIDI channel numb

For this purpose all we need is the control value.

Depending on what the value of the parameter you are trying to control you will have to multiply or divide the maximum

value by something so you have full control of the parameter. For example for my Mod index controller i have a range of 0-

2000 on the output range of my [vslider]. so if i divide that by 127 i get 15.74 which is the number i must multiply the MIDontrol value by, in order to have full control of my [vslider]. Once i have my [ctlin 9] wired to a number box and multi-

plied by the correct amount it is sent to the [vslider] to control its movements.

As it requires you to press the messages in the order they

are listed (i.e open,start,stop.) i routed some bangs to the

GUI and made them traffic light colors to make it more ob-vious to new users .

By introducing a [save-

panel] object and a bang fol-

lowing to trigger the open

message, i am now able to

choose the directory to make

the sound file and decide

what to name it each time.

This is much more useful than

having the file named the

same every time as is the case

with incorporating the file

name and directory within the

open message e.g [open

../desktop/sample1]


7/8

Conclusions And Developmental Ideas.

6

I am quite happy with how this project has worked out so far, but i will indeed keep developing this patch as there are a

few thing i would like to see included as and when i discover how to do them. Firstly i would like to include multiple

voices so it is possible to play chords. I found this quite a conundrum as i could not work out how to get multiple oscilla-

tors to for example, all take the drawn wave shape that the user has inputed into the [tabosc4~] table and mirror it in

other hidden tables to create multiple voices. Needless to say this would add a lot more to the sound and capabilities of

the synthesizer.

Another thing i would like to add, would be the option to mix back in the unfiltered signals from both of the oscillators

as well just to add to the array of sounds that it can make.

Of course you can never have too many oscillators i expect as i develop it further it will gain many more and

grow considerably in size.

I am very interested in creating synthesizers that combine various methods of synthesis, so one of the features i will be

adding is an oscillator that combines the two forms of synthesis in this patch in one. i.e Wavetable and Frequency modu

lation synthesis. In a way its a shame i am thinking of this now in hindsight as it would have been good to include in this

first version, and i am quite capable of doing it by simply replacing the carrier oscillator in my FM module with an edit-

able wave table oscillator such as the [tabosc4~] used in the wavetable module in this version.

Overall i think my patching could do with a few more sends and receives and, throws and catches to neaten thing up a

bit but i have had a lot of fun building this instrument and i am sure i will have much more fun in the future fixing

things, and of course going back into the parts of the code that are borrowed from external sources and making them

more my own as i get more confident with my skills and some more crazy ideas start coming into my head.


8/8

7

Under The Hood. (Patch window)

james truscott - sound design 1 (mu316)

Documents