Envelope follower is the name for a device used in musical electronic environments that detects the amplitude variation during time of an incoming sound and produces a control signal that resembles it. Usually it offers the possibility to modify the attack and the release stages of the output signal.

It can be useful to drive an amplification stage to modify the amplitude time variation (Envelope) of the incoming sound or to relate other sounds amplitude to it, but can be also used to modify certain parameters of other controllable devices (Filters, Wave shapers etc.) in relation with the incoming signal's amplitude.

Envelope followers exist as hardware devices as well as software devices.