envelope follower

An envelope follower is a circuit that tracks the dynamics of a player's picking and uses that signal to control another function, such as a voltage controlled filter¹. It is the basis of auto-wah or envelope filter effects, as in the Lovetone Meatball, which features an envelope trigger, also called an envelope follower filter². The Mu-Tron III consists of an envelope follower that uses optocouplers to control a voltage controlled filter¹. Envelope followers also appear as features in other pedals, such as the pick-attack envelope follower functionality in the EarthQuaker Devices Night Wire³, the envelope follower for wah wah sounds in the Dreadbox Disorder⁴, and as an LFO shape option in several modes of the Electro-Harmonix Mod 11⁵.