The Duo is an Organ and Drum duo. Adding in the bass of Mike was very cool to hear. Though they probably played a bunch of original stuff, I don't really know there music all that well. Most of it just seemed like they were jamming around.
They did a number of cover's including Yes's Roundabout along with Foam by Phish. They also finished with Phish's tune Mike's Song as the encore. For this one, it was the crowd on vocals (though I hear Mike has been singing it at some shows).
The show was very cool. Interesting music and a cool crowd (as is usually found at jam shows). If you'd like to hear the music they created, you can download it here.