Resets specific controllers to default states. In general, switches (such as Hold Pedal) are turned off, and continuous controllers (such as Mod Wheel) are set to minimum positions. If the device is MultiTimbral, this only affects the Part assigned to the MIDI channel upon which this message is received.
For a minimum implementation of "All Controllers off", it is recommended that the following controllers should be reset to the following values:
Modulation Wheel should be set to 0.
Expression should be set to full value (ie, 127 for both coarse, as well as fine if used).
The pedals Hold, Portamento, Sustenuto, Soft, Legato, and Hold 2 should be set to 0 (ie, Off).
Volume should be set to 100.
Pan should be set to center (ie, 64 for both coarse, as well as fine if used).
Any Non-registered Parameters or Registered Parameters may be reset to default values, such as pitch bend range being reset to +/- 2 semitones.
Additionally, the Pitch Wheel should be reset to center position, and Channel Pressure should be set to 0, although these technically aren't adjusted via MIDI controller messages. If a module supports Aftertouch, then the Aftertouch amount for each note (on the MIDI channel) should also be reset to 0.
A device should not reset its mode (as done via Omni Mode Off, Omni Mode On, Mono Operation, and Poly Operation controllers).
A device should include documentation that lists what is reset by an All Controllers Off message.
The value byte isn't used and defaults to 0.