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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.