Sonic Pi is described as 'Soinc Pi is a live-coding audio software. Learn to code creatively by composing, improvising or performing in an incredible range of styles from classical through to algorave' and is a music production app in the audio & music category. There are more than 10 alternatives to Sonic Pi for a variety of platforms, including Web-based, Windows, Self-Hosted, Mac and Linux apps. The best Sonic Pi alternative is strudel, which is both free and Open Source. Other great apps like Sonic Pi are SuperCollider, AudioMasher, Web Audio Studio and Faust.
The SOUL platform is a language and an API. The language is a small, carefully crafted DSL for writing the real-time parts of an audio algorithm. The API is designed to deploy that SOUL code to heterogeneous CPUs and DSPs, both locally and remotely.
Wavepot is a live-coding environment for creating sound and music. Build sound and music compositions on-the-fly using JavaScript and save your projects right to GitHub.
Nyquist is a language and IDE for sound synthesis and music composition. It is implemented in C and C++ and runs on Win32, OSX, and Linux. Nyquist combines a powerful functional programming style with efficient signal-processing primitives.
Evaluator is an audio creation app that lets you write short C-style programs whose output is used to generate sound! It's available as a standalone app or as a VST plugin for your DAW.
Extempore is a programming language and runtime environment designed to support the programming of real-time systems in real-time.
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Extempore doesn't seem to be about programming music.