We've seen a number of examples of audio performances getting a boost from surface computing. There's the ReacTable, which is probably the most well known from Bjork's performances. There's also the reacTagon and many others too numerous to name. On Microsoft Surface there is Stimulant's work on ToneGrid and VectorForm's Surface DJ.
In the past, we covered Kevin Kennedy's work on a VJ application called SplatBox.
(By the way, if you're naming an app like this, make it one word, caps in the second part of the word and you'll be golden.)
Now, breaking onto the scene of VJ applications is Microsoft Research in Cambridge with their really cool application called VPlay. Covered here on Ars, the application brings the isolating task of mixing video real-time with computers into the collaborative space of surface computing. It uses digital objects that represent content and mixing effects to give an interactive and "new each time" feel to the output on the screen. You can also view the project information and research paper. Enjoy!
VPlay Developer Interview
Designers and developers, keep up the great work on these new computing interactions.