U.S. version
The Office, the one with Steve Carell, has a very lively opening tune that starts with the piano. The opening credits scenes evolve from time to time, and up until the fourth season, it played before the show. Onwards it played over the closing credits which previously rolled in silence.
The theme song was written by American composer Jay Ferguson, and performed by The Scrantones—as in Scranton, Pennsylvania, where the show is set. I believe there is no commercially available original recording of this tune.
Watch & listen