Modulation

1. In general, periodic variation of a waveform, in which some aspect of the waveform is varied usually according to the instantaneous value of some other waveform. The waveform being varied is often called the “carrier”, while the waveform that controls the modulation is itself often called the “modulation”. Many mathematically specified types of modulation exist, such as amplitude modulation and frequency modulation.
2. MIDI controller message type number 1, which conventionally instructs the receiver to apply an LFO to the frequency of the generated waveform in order to produce vibrato. By long-standing convention, this message type is associated with the mod wheel performance control.