In this YouTube Video, I demonstrate how to use Ableton Live 8 and the Velocity MIDI device along with a dummy clip to add velocity to incoming MIDI notes that are a fixed velocity. I illustrate this with the Tenori-On but this concept will work with any MIDI device.
Once velocity is introduced into the equation you can then do all sorts of interesting things with modulation. In the video I use velocity to modulate the filter frequency with Circle. Of course you could just as easily use this to play different samples in a velocity split with Sampler and so on.
Update: Note this same technique will also work for adding notes to incoming MIDI from User Mode 1 from a Novation Launchpad which is also fixed velocity.
Electronic Music Artist, Composer, Sound Designer