Rax is a virtual synth/effect rack for Audio Units.
You can create as many racks as you like and use them simultaneously. Each rack can respond to a different MIDI source or the same MIDI source on different MIDI channels or the same MIDI source on the same channel for fat sounds. Any v2 AU effect can be loaded into a rack. The signal is processed in a top down direction.
Note this is a very preliminary release and is not intended for real applications.