With Local Control on, playing a synthesizer or sampler does two things: it triggers built-in sound generators and sends data to the MIDI Out. With Local Control off, the keyboard still sends data to the MIDI Out but does not drive the internal sound generators, which now respond solely to data appearing at the MIDI In. In other words, Local Control off disconnects a synthesizer’s keyboard from its sound generator, while leaving them both active for MIDI purposes. See MIDI mode.