Yeah. It's called "Wedding Bells" and it was the surprise ending of yesterday's Apple circle-jerk. Of course Steve brought Chris Martin in to play a few songs, he named his kid after the company!
Martin admits the song may never appear again, so take it for what it is... a pseudo-crappy performance by Chris Martin and a piano. He also played "Yellow", which I wish we had on video BUT WE DON'T. He also played "Viva La Vida" which I snore.