MIDSensor is a basic but powerful program which lets you control MIDI gears with mouse or joystick moves in 2 Dimensions. Select 1 or 2 preset or programmable continuous controller and start waving upon the window!
Used in conjunction with a Yamaha RM1x sequencer/expander to modulate sounds in real-time. Should work well with Roland MC303-505 and all MIDI gears that deals with Continuous Controllers (at least Pan and Volume). All the MIDI events are recordable.