Overtone

Overtone is:

Overtone is an open source audio environment designed to explore new musical ideas from synthesis and sampling to instrument building, live-coding and collaborative jamming. We combine the powerful SuperCollider audio engine, with Clojure, a state of-the-art lisp, to create an intoxicating interactive sonic experience.

Like TidalCycles based on SuperCollider, but instead it uses Clojure and can mesh well with Quil which uses Processing under the hood.