Create audio plugins on-the-fly with LuaJIT.
Protoplug is a scriptable plugin that lets you load and edit Lua/LuaJIT scripts as audio effects and instruments. The scripts can process audio and MIDI, display their own interface, and use external libraries.
Cross-platform: builds for Windows, Mac OS X and Linux. This means that all protoplug scripts are compatible with these platforms and can be loaded into a huge amount of audio software (glory to JUCE).
Fast: Use the speed of LuaJIT, and perform DSP tasks as efficiently as old school C implementations.
Free and open source: Want a new feature? Add it yourself. The source is MIT-licensed and available on Github.