A MIDI Controller message that controls the ability of a synthesizer to be played by means of its own keyboard.The local control message has one parameter, which may be an "on" or "off" value. When a synth with a keyboard receives a local control off message, the sound-producing part of the synth, and the keyboard and ancillary performance controls (pitch wheel etc.) behave as two separate units. Pressing a key will not produce a sound but will send messages out of the MIDI out port, while the sound-producing part of the synth will produce sound only in response to messages coming in through the MIDI in port. Receiving a local control on message restores normal operation. The local control capability facilitates use of the synth’s keyboard as a master keyboard for controlling other synths (particularly rackmount synthesizers which lack keyboards of their own); it prevents the synth from sounding when the keyboard is being used to control another synth (without the necessity of selecting a “silence” patch). This is particularly useful for recording with a sequencer or DAW; generally in this type of setup local control is off and the user selects the synth to be played using the sequencer’s soft thru capability. (This could in fact be the synth with the keyboard, but with local control off, the notes have to go through the sequencer and back via MIDI.)
The controller message in question is of type 122. An data byte value of 127 tells the receiver to turn local control on; a value of 0 is for local control off.