Programming Sound with Pure Data

Building an Envelope

Whereas the LFO is a tool for creating repeating motion in a sound, an envelope is for creating single motion events. The name “envelope” comes from the analogy of opening and closing a paper envelope, so an envelope is generally for increasing some parameter and then at a later time decreasing it. A common use is to increase and decrease the volume of a signal over time. We’ll use this envelope in almost every patch we make from the next chapter until the end of this book, and you’ll find this to be a valuable tool in your own patches.

Designing an Envelope

We’ll build a subpatch that matches the specs of a classic ADSR envelope. That stands for attack, decay, sustain, and release. Envelopes can have more or fewer parameters ...