Ingen

Screen dump: 
Various modules connected up together within ingen

Ingen is a modular audio processing system for GNU/Linux audio systems using the Jack audio server and LV2 or LADSPA plugins. It can be used to create modular synths by using synth plugin modules.

Any saved Ingen graph can be loaded as an LV2 plugin on any system where Ingen is installed. This allows users to visually develop custom plugins for use in other applications without programming.