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A MIDI Primer

Multimedia Articles

Written by TParker

Tuesday, 31 August 2004

Article Index
A MIDI Primer
Electronic Musical Information
The MIDI Interface
Using MIDI THRU
The MIDI Channels
Using MIDI Patchbays
MIDI Sequencing and Synchronization
The Anatomy of a MIDI Message
Limitations of MIDI
MIDI 1.0 Specification

Page 10 of 10

MIDI 1.0 Specification

The following is an excerpt of the official MIDI 1.0 Specification. You may order the complete specification, which includes General MIDI, Standard MIDI, and more from the

MIDI Manufacturers Association. The information on this page is presented for reference only and does not supercede the official specification. Obviously, it isn't necessary to learn all of this stuff to make excellent use of MIDI. But, looking over this will help you get a good grasp of what MIDI is doing through that little round cable. MIDI messages can be just about anything - pitch bend, modulation, aftertouch, key pressure, breath controller, foot pedal, program changes and much, much more. Please scroll down this page to view the MIDI 1.0 specification.

Status	Data Byte(s)	Description
D7----D0	D7----D0

Channel Voice Messages
1000cccc	0nnnnnnn	Note Off event.
	0vvvvvvv	This message is sent when a note is released (ended). (nnnnnnn) is the note number. (vvvvvvv) is the velocity.
1001cccc	0nnnnnnn	Note On event.
	0vvvvvvv	This message is sent when a note is depressed (start). (nnnnnnn) is the note number. (vvvvvvv) is the velocity.
1010cccc	0nnnnnnn	Polyphonic Key Pressure (After-touch).
	0vvvvvvv	This message is sent when the pressure (velocity) of a previously triggered note changes. (nnnnnnn) is the note number. (vvvvvvv) is the new velocity.
1011cccc	0ccccccc	Control Change.
	0vvvvvvv	This message is sent when a controller value changes. Controllers include devices such as pedals and levers. Certain controller numbers are reserved for specific purposes. See Channel Mode Messages. (ccccccc) is the controller number. (vvvvvvv) is the new value.
1100cccc	0ppppppp	Program Change. This message sent when the patch number changes. (ppppppp) is the new program number.
1101nnnn	0ccccccc	Channel Pressure (After-touch). This message is sent when the channel pressure changes. Some velocity-sensing keyboards do not support polyphonic after-touch. Use this message to send the single greatest velocity (of all te current depressed keys). (ccccccc) is the channel number.
1110nnnn	0lllllll	Pitch Wheel Change.
	0mmmmmmm	This message is sent to indicate a change in the pitch wheel. The pitch wheel is measured by a fourteen bit value. Center (no pitch change) is 2000H. Sensitivity is a function of the transmitter. (llllll) are the least significant 7 bits. (mmmmmm) are the most significant 7 bits.

Channel Mode Messages (See also Control Change, above)
1011nnnn	0ccccccc	Channel Mode Messages.
	0vvvvvvv	This the same code as the Control Change (above), but implements Mode control by using reserved controller numbers. The numbers are: Local Control. When Local Control is Off, all devices on a given channel will respond only to data received over MIDI. Played data, etc. will be ignored. Local Control On restores the functions of the normal controllers. c = 122, v = 0: Local Control Off c = 122, v = 127: Local Control On All Notes Off. When an All Notes Off is received, all oscillators will turn off. c = 123, v = 0: All Notes Off (See text for description of actual mode commands.)
		c = 124, v = 0: Omni Mode Off
		c = 125, v = 0: Omni Mode On
		c = 126, v = M: Mono Mode On (Poly Off) where M is the number of channels (Omni Off) or 0 (Omni On)
		c = 127, v = 0: Poly Mode On (Mono Off) (Note: These four messages also cause All Notes Off)
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System Common Messages
11110000	0iiiiiii	System Exclusive.
11110111	0ddddddd	This message makes up for all that MIDI doesn't support. (iiiiiii) is a seven bit Manufacturer's I.D. code. If the synthesizer recognizes the I.D. code as its own, it will listen to the rest of the message (ddddddd). Otherwise, the message will be ignored. System Exclusive is used to send bulk dumps such as patch parameters and other non-spec data. (Note: Real-Time messages ONLY may be interleaved with a System Exclusive.)
11110001		Undefined.
11110010	0lllllll	Song Position Pointer.
	0mmmmmmm	This is an internal 14 bit register that holds the number of MIDI beats (1 beat=six MIDI clocks) since the start of the song. l is the LSB, m the MSB.
11110011	0sssssss	Song Select. The Song Select specifies which sequence or song is to be played.
11110100		Undefined.
11110101		Undefined.
11110110		Tune Request. Upon receiving a Tune Request, all analog sythesizers should tune their oscillators.
11110111		End of Exclusive. Used to terminate a System Exclusive dump (see above).
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System Real-Time Messages
11111000		Timing Clock. Sent 24 times per quarter note when synchronization is required (see text).
11111001		Undefined.
11111010		Start. Start the current sequence playing. (This message will be followed with Timing Clocks).
11111011		Continue. Continue at the point the sequence was Stopped.
11111100		Stop. Stop the current sequence.
11111101		Undefined.
11111110		Active Sensing. Use of this message is optional. When initially sent, the receiver will expect to receive another Active Sensing message each 300ms (max), or it will be assume that the connection has been terminated. At termination, the receiver will turn off all voices and return to normal (non-active sensing) operation.
11111111		Reset. Reset all receivers in the system to power-up status. This should be used sparingly, preferably under manual control. In particular, it should not be sent on power-up.

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Last Updated ( Wednesday, 24 August 2005 )

Studio Jargon

Equal Temperament

A system for dividing an octave into 12 pitch steps, each of 100 cents. This has the effect of making all semitones equal in size. This became necessary once keyboard and fretted instruments became popular. It should be understood that the note A which appears in F# minor should have a slightly different frequency from the note A which appears in C major (this fine distinction is one of the reasons that pitch and frequency are not quite synonymous). This would normally be dealt with automatically by a proficient player on an instrument with continuous pitching such as a violin. A keyboard instrument would properly have to be tuned to a particular key, if music was then played in a different key, some or many of the intervals sounded would be flat or sharp. However since it was not convenient to retune these types of instruments correctly whenever a new key was required, various compromises were attempted. Equal temperament was one such compromise whereby the error was distributed equally between all the notes. This made the performance of music in different keys possible on the same instrument without retuning, in celebration of which J. S. Bach wrote not one, but two books, each of 24 preludes and fugues (a prelude and fugue in both the major and minor forms of 12 keys).

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