Often abbreviated PWM, pulse width modulation is a method of modifying a periodic signal based on some characteristic of another signal. The concept is similar to FM (Frequency Modulation) only instead of the frequency of some steady periodic signal being altered, the signal itself is not steady. It’s in the form of pulses, where the width or duty cycle of the pulse is altered. In synthesizers PWM is used to produce sounds that vary in timbre based on the action of the modulation source (could be velocity, LFO, a wheel, or some other continuous controller). This occurs because the harmonic content of a signal necessarily changes as its duty cycle changes. In industrial equipment PWM is sometimes used as a method of regulating power. For example, shorter duration pulses that are each at a fixed power level produce less net power overall.