Structure of MIDI Messages

MIDI Messages

Channel

System

Mode

Voice

Real Time

Common

System Exclusive

Channel messages

Have up to 3 bytes. The first byte is the status byte.

This type of channel message controls voice. Sends information specifying which note to play

or to turn off. Encodes key pressure. Voice messages are also used to specify

controller effects such as sustain, vibrato, tremolo and the pitch wheel.

Voice messages

Voice messages

1st byte: Status byte

2nd byte: Pitch Data byte

3rd byte: Velocity Data byte

Note On

To end a note, with particular pitch, on a particular channel.

The 1st byte (status byte) is 1000cccc. Note off message will stop a presently playing

note of the same pitch.

Note Off

Control Change Assigns some effect to the sound in the channel.

1st byte: Status byte 1011cccc 2nd byte: control change type 0ddddddd 3rd/4th byte: control change value 0ddddddd

Assign particular patch (instrument) to a channel.

Synthesizers have assigned “program numbers” to each patch.

The manufacturer decides how to assign which number to which patch.

1st byte: Status byte 1100cccc

2nd byte: program number data byte 0ddddddd

Program Change

Polyphonic Key Pressure

Messages are transmitted by instruments that are capable of

playing more than one sound at a time.

Pressure messages

Used to alter the sound of notes while they are playing.

Pressure is also called aftertouch.

Channel mode messages

Special case of the control change message All mode messages have opcode B. The message is &Hbn or 1011nnnn. The difference between a control message and a channel

mode message is in the first data byte. Channel mode message has its first data byte in 121 through

127 (&h79-7f). Channel mode messages determine how an instrument

processes midi voice messages. Respond to all messages. Respond just to the correct channel. Don't respond at all.

MIDI mode messages

System messages have no channel number. They are not channel specific. Timing signals for synchronization, positioning

information in pre-recorded MIDI sequences and detailed setup information for the destination device.

Opcode for all system messages start with &HF. System messages are divided into 3

classifications. i) system common messages ii) system real time messages Iii) system exclusive messages

System Messages

MIDI system common message

Song position is measured in beats beat is defined as the length of a specific

note. System Common messages are intended for

all receivers in the system.

The MIDI System Real Time messages are used to synchronize all of the MIDI clock-based equipment within a system, such as sequencers and drum machines.

MIDI System Real Time messages

System exclusive message

The MIDI standard can be extended by manufacturers.

After the initial code, a stream of any specific messages can be inserted that apply to their own product.

A System Exclusive message is supposed to be terminated by a terminator byte &HF7

The terminator is optional and the data stream may simply be ended by sending the status byte of the next message.