In music production, an envelope follower is a signal processing technique that extracts the contour or shape of an audio signal’s amplitude envelope and applies it to another parameter or effect. The envelope follower analyses the amplitude of an incoming signal and generates a control signal that follows the changes in the amplitude envelope.

The control signal generated by the envelope follower can then be used to modulate other parameters of a sound or effect, such as filter cutoff frequency, volume, or modulation depth. For example, an envelope follower can be used to apply a filter to a sound that is triggered by the level of another sound in the mix, creating a sidechain compression effect.

Envelope followers are often used in electronic music genres like EDM, where they are used to create rhythmic effects and modulation. They can also be used in mixing and mastering to control the dynamics of a mix and shape the sound of individual tracks.

Overall, the envelope follower is a powerful tool for music producers and sound designers, allowing them to extract and apply the dynamic and expressive qualities of an audio signal’s amplitude envelope to other parameters or effects, creating unique and interesting sounds and effects.