I distinctly remember a KB with such a feature being announced at one point, but I've no details on what manufacturer or if the model ever gained any momentum.
I believe that the one I had in mind was the Continuum; mentioned & linked by Jeff in Post #4. Relatively expensive, but considering the feature set, it's not much more than a high-end hardware synth.
... unlike aftertouch which conflicts too much with velocity IMO (plus AT is implemented really badly on the three controllers I've had personal experience with).
The best I've ever used was in the (original) Novation ReMote controllers.
Very expressive. But I've run the gamut. Perhaps the worst implementation is in my AKAI Max49. Down pressure is passable; release snaps between 4-5 values of 128.
I have recently added a ribbon controller to my Kurzweil PC3K and it is quite amazing.
What's the manufacturer/model, Jeff? I consider the Doepfer R2M every time I look to order another Wheel Electronic kit.
I've never used an expression pedal/controller and don't really know what it does. I imagine it's similar to volume automation?
I consider it essential; along with a sustain pedal. While it's intended to vary expression in overall volume, it doesn't have to be used that way. In most controllers and synths, it can used to point at many different parameters. I'll use it for filter cutoff, unidirectional pitch bend, sequencer depth, ... most anything that I don't have a free hand for.
Not to detract from Mike's tutorial here. I found it to be an excellent primer, and I look forward to Part II. The subject did open up an interesting discussion. I don't think that many of us - end users or manufacturers - ever fully utilize the expressive capabilities built into MIDI over 30 years ago.