What is MPE?
The latest KVR Audio videos feature Peter Nyboer answering this question, and offering an introduction to MIDI Polyphonic Expression (MPE).
MPE is a recently adopted standard that supports new options for expressive music performance using MIDI devices and software. MPE is a method of using MIDI which lets you use multidimensional controllers to control multiple parameters of every note within MPE-compatible software.
Traditionally with MIDI, expressive controls like Pitch Bend are applied to all notes being played. In MPE, each note is assigned its own MIDI Channel, which allows expressive controls like Pitch Bend to be applied per-note.
More info is available at the MIDI.org site.
Are you using MPE? If so, share your set up in the comments!