The part of a synthesizer that tells the sound generators and controllers what to do to make a given note. These modules include envelope generators, LFOs, the keyboard itself, and the modulation and pitch-bend wheels. These allow control of some aspects of a synthesizer’s sound by sending signals to the sound generators and modifiers telling them now to behave. For instance, the keyboard sends a signal to the oscillator telling it what frequency to play. Also called modulation modules.