Steve Lacey over at Random Thoughts points to this intriguing music software, Reason. He thinks it could be a great Tablet PC app as the interface that allows you to build and design sound systems in "a very graphical sense." You add components to your tasted to get the sound you want and plug and play with the different components. Typically done with the mouse, Steve sees no reason the pen can't do the same.
The pic shows it on his Tablet PC.
Here's a link with a neat video trailer of the software.