I found these great videos while digging around Hackaday recently:

Imogen Heap performs "First train home" on Letterman.

Shes using a Monome in her lap throughout the performance.
Some of the buttons are sounds, some are patch triggers for the laptop, and some are audio effects and filters (also performed by the laptop) for her mic.

She has always had a beautiful voice. Its always nice to reconnect to an artist I used to like 'back in the day.'