Gate

A signal which conventionally represents the pressing and releasing of a key on a keyboard, or some other on/off state, and is most commonly used to activate an envelope generator. Conventionally, a gate signal has two states. When no keys are pressed on the keyboard, the gate is in the low or inactive state. Pressing a key changes the gate signal to the active or high state, and it remains in that state as long as the key is pressed. (See ADSR for a description of how a typical envelope generator uses a gate signal.) The gate signal is by definition monophonic; on a monophonic synth, generally the gate signal will be in the high state as long as any key on the keyboard is pressed. However, true polyphonic synths extend the concept so that a gate signal exists (conceptually if not in actual implementation) for each voice. Gate signals can also represent the state of switches and other events with two states. Compare with trigger.