zynaddsubfx 2.4.0-1build2 (i386 binary) in ubuntu maverick

 A real-time software synthesizer for Linux and Windows with many
 features, including polyphony, multi-timbral and microtonal
 capabilities. It includes randomness of some parameters, which
 makes warm sounds, like analogue synthesizers.
 It has system/insertion effects too, and much more.