Synesthesia is VJ software for making audio-reactive visuals. It draws from the Shadertoy community, where everything is made with GLSL fragment shaders, but includes an easy way to add audio and video inputs and build simple MIDI-mappable control interfaces. Basically, everything a VJ needs to actually perform live with some shaders. The folks building Synesthesia seem super respectful of free-sharing ethos of Shadertoy -- they reached out to shader programmers like me and comissioned new works for Synesthesia, while keeping the actual shaders always hackable by users within the application. I wound up making a few fun video feedback and cellular-automata based scenes, and recently was goaded into using some of them to mess up the live stream from an algorave concert at the AIMC conference: