General MIDI System Enable Disable message

A MIDI event that carries the General MIDI (GM) system enable / disable message tells a MIDI device to enable or disable the GM sound module or GM patch set.

The General MIDI (GM) system enable / disable message is a universal non-real time system exclusive message (a system exclusive message which all MIDI devices should consider, but not necessarily immediately). System exclusive messages belong to the category of MIDI system common messages.

MIDI devices may have sound modules and patch sets that are General MIDI compliant and some that are not compliant. When GM becomes enabled, however, it overwrites non-GM compliant modules and thus the MIDI device becomes GM compliant. Thus, the device can go beyond the GM protocol, but still be compliant when it needs to.

The GM system enable / disable message has the following format.

0xF0 0x7E 0xid 0x09 0xnn 0xF7

0xF0 is the message status byte and shows that this is a system exclusive message. 0x7E shows that this is a universal non-real time system exclusive message. All devices should consider this message, but not necessarily immediately. 0xid is the system exclusive channel, usually the manufacturer ID (see MIDI System Exclusive message), but could be any value from 0x00 to 0x7F (from 0 to 127), where 0x7F prompts all devices to respond. 0x09 and 0xnn are the sub ID of the universal system exclusive message. 0xnn could be 0x00 or 0x01. 0x09 0x00 show that this is a “GM disable” message. 0x09 0x01 shows that this is a “GM enable” message. 0xF7 denotes the end of the system exclusive message.

The following is an example of a GM system enable / disable message.

0xF0 0x7E 0x7F 0x09 0x01 0xF7

0xF0 shows that this is a system exclusive message. 0x7E shows that this is a universal non-real time system exclusive message. 0x7F is the system exclusive channel and in this case shows that all MIDI devices should respond to this message. 0x09 0x01 shows that this is a GM enable message. 0xF7 denotes the end of the system exclusive message.

See also:
Musical Instrument Digital Interface (MIDI)

Comments

admin: First posted on 2014 07 22

anonymous, 2014 07 22: "0x09 0x01 shows that this is a “GM disable” message." "0x09 0x01 shows that this is a GM enable message." A bit contradictory, isn't it? ;)

mic, 2014 07 22: Thanks. This is a mistake. 0x00 is disable, 0x01 is enable. I have fixed it.

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