In the Music Studio showcase at Macworld/iWorld on Saturday, Stefan Lipson gave the audience a look at KaleidoPro, a MIDI application that works with a drum controller or any MIDI instrument. With KaleidoPro, a musician can play not just a wide range of drum kits, but also other instruments.
Musicians can map different sounds on the drum pad, which is connected to a Mac. You then create a composition that tells the software how to process the MIDI data. When you're actually performing, the data is processed in real-time.
Now, I realize what I wrote may not make sense to a lot of people--heck, I'm not even sure I understand it myself. So it's probably best to just watch the video below to see what KaleidoPro can let you do.
KaleidoPro for Mac is $49. The software works with different MIDI controllers, though you cab use a keyboard and mouse to play."