From WikiAudio

MIDI channel messages have 7 messages which are defined by the first three bits after the first bit of the status byte (they are listed here). However, there are 8 values that are available. The 8th value is 1111000. This value denotes a MIDI system message. These are messages that affect the entire MIDI module receiving the message and are not channel based.Therefore the last four bits of the status byte are used to define the type(s) of system message.

Contents 1 MIDI system messages 1.1 Common 1.1.1 Tune Request 1.1.2 Song Select 1.1.3 Song Position Pointer 1.1.4 MIDI Time Code 1.1.5 System Exclusive 1.1.5.1 1.1.5.2 Start of Exclusive F0 1.1.5.3 Manufacturer ID# 1.1.5.4 Product ID# 1.1.5.5 Device ID# 1.1.5.6 DATA 1.1.5.7 End of Exclusive F7 1.2 Real-Time 1.2.1 MIDI Beat Clocks 1.2.2 Start 1.2.3 Stop 1.2.4 Continue 1.2.5 Active Sensing 1.2.6 System Reset

MIDI system messages

Common

Tune Request

Status byte: 11110110

Tune request is a MIDI message intended to be a simple way to tune the oscillators of an analog synthesizer. Upon receiving this message an analog synthesizer that responds to it will tune its oscillators. This MIDI message was created during an era where many analog synthesizers would drift out of tune easily.

Song Select

Status byte: 11110011

The Song Select message specifies which sequence or song is to be played (usually pertains to a MIDI sequencer)

Song Position Pointer

Status byte: 11110010

Song Position Pointer is an internal 14 bit register that holds the number of MIDI beats (1 beat= six MIDI clocks) since the start of the song (in a MIDI sequencer).

MIDI Time Code

Status byte: 11110001

The easiest way to think of MIDI Time Code (or MTC) is a digitized form of SMPTE timecode. MTC is used to either synchronize different MIDI sequencers, or as a way to convert SMPTE time code to a digitize language that a MIDI sequencer can recognize. MIDI Time Code is an absolute timing reference. This is in contrast to MIDI beat clocks which is a relative timing reference.

Each MIDI Time Code message is a quarter frame synchronization message.In other words for every SMPTE frame that passes four MIDI Time Code messages will have been sent. The quarter frame message status byte is accommodated by one data byte that contains the SMPTE time (hours,minutes,seconds,frames).

System Exclusive

Start of Exclusive F0

Manufacturer ID#

Product ID#

Device ID#

DATA

End of Exclusive F7

Real-Time

MIDI Beat Clocks

Start

Stop

Continue

Active Sensing

System Reset

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