MIDI system realtime messages


The MIDI protocol consists of MIDI events that carry four types of messages: 1) voice messages; 2) system common messages; 3) system realtime messages; and 4) meta messages.

While MIDI voice messages are specific to a MIDI channel, system common and system realtime messages are not specific to a channel and thus all MIDI devices on the MIDI system should respond to such messages. Thus, these messages are "system" messages. Some of these system messages provide require response in real time and are called "system realtime" messages. The rest are "system common messages".

MIDI system realtime messages are messages that are not specific to a MIDI channel but prompt all devices on the MIDI system to respond and to do so in real time.

The following messages are MIDI system realtime messages.

Message MIDI device action
MIDI clock Understand the position of the MIDI clock when synchronized to another device
Start Start playback of the current MIDI sequence
Continue Resume playback of the current MIDI sequence
Stop Stop playback of the current MIDI sequence
Active sense Understand that a MIDI connection exists (when there are no other MIDI messages)
Reset Reset to default state

A MIDI system realtime message – usually the MIDI clock message – can be placed in the middle of another message without affecting this other message or changing the MIDI running status. The realtime message can be recognized and handled appropriately, because its status byte has a topmost bit equal to 1, whereas the bytes of MIDI message data after the status byte have topmost bytes equal to 0, and because the length of system realtime messages is known.

See also:
Musical Instrument Digital Interface (MIDI)

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I have not seen anything that explicitly states whether these can be in MIDI files (the Reset message cannot - the same status byte is used for meta messages). But putting these in presents a logistical nightmare. For example, if a sequence reaches a Stop message, are the remaining messages reachable?
Posted At 12-01-2017 08:03:44

can system realtime messages be really stored in midi file? or are they just sent by user request
Posted At 11-01-2017 01:41:43

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