Bob Currie [Cakewalk]
IOW, the pen will do "coupled-drawing" (via pen pressure) in whatever lane is highlighted in the controller pane.
FWIW, we're still getting our arms around how the pen could be used in SONAR. Although pens have been around for a while, even Microsoft is still grappling with how they can and should be used in applications.
Pens, for me anyway, are useful in a couple of situations. The first is when you need pixel-level precision or close to it. They're easier to manoeuvre than a mouse for the same reason it's easier to write holding a pen in your fingers than it is to write with a sharpie glued to the palm of your hand.
This is particularly true on touch screens where it can be very difficult to only affect the pixels you want affected, fingers are blunt instruments for that kind of job.
The second situation kind of ties in with the first. Pens are pressure-sensitive, so pressure can be used to do things as well as positioning. The obvious use for this is in graphics applications, and I suppose might translate into a DAW by using pressure to e.g. define velocity while drawing notes. Trouble is pressure can be very difficult to apply absolutely consistently.
I agree MS (or Apple) have't really worked out what to do with the "third interface dimension" of pressure. Apple have pressure sensitive touchpads, and I'm using one at the moment, but uses for the pressure sensitivity in software are limited and the pad doesn't really replace a graphics tablet and pen for precise work. There's also the Apple pen for the iPad Pros but it's essentially still a graphics tool.
I guess what I'm saying is a pen would be very useful for touch-screen work for accuracy, but the role of a pressure function would have to be considered very carefully before activating it. Kind of how a very sensitive keyboard aftertouch can be a pain to work with because it's too difficult not to send aftertouch when you don't intend to.