Envelope following is an interesting way to modulate a parameter based on an incoming signal. All Noise Engineering effects plugins have envelope following as a built-in modulation source, so today we’ll be talking about what envelope following is, and show an example of how we can use it to liven up a drum loop with our free Ruina distortion plugin.

What is envelope following?

An envelope follower is a simple utility that turns an incoming audio signal into a control signal by tracing its amplitude as it plays. Envelope followers are used in many types of audio processing, from compressors used in mixing to autofilter pedals. We added envelope followers as a modulation source that can be routed to any number of parameters, since they’re a wonderful way to add movement and variation to a sound in a very organic way.

A drum loop with an outline of its volume envelope

Routing the envelope follower in Ruina

For this example, we’ll be using the envelope follower to modulate the Fold and Overdrive parameters in Ruina to dynamically change the timbre of a drum loop. To route the envelope follower to a parameter, simply right-click (or control+click on Mac) the slider, and turn up the Index slider labeled Env. The Index control here will set the maximum modulation range. Since incoming audio will vary in level, the sensitivity of the envelope follower can also be adjusted by navigating to the Env tab under Modulation and changing the main Index slider there.

Ruina's envelope follower routed to the wavefolder and scaled with the Index controls

How it sounds

As you can hear in the example below, envelope following creates some dynamic timbral shifts in our sound: the louder the sound going into Ruina, the more the Fold parameter is turned up, and the more extreme the wavefolding.

Of course, this is just a single application of envelope following: the envelope follower can be routed to any parameter (or suite of parameters), and can be used in any Noise Engineering effect. I like to route the envelope follower to negatively modulate the Blend parameter in Desmodus, creating swells of reverb when incoming audio is silent. Experimenting with envelope following is always a good time!