Please help me with a friends episode and song ?????

There is an episode in which the 6 of them are at the coffee house doing different things (ie: reading, crossword puzzle, eating) and Ross starts the tune of a song. The others then join in and at one point Chandler (holding a pencil) does a kind of drum thing. After they finish that song Ross then starts the "I Dream of Jeanie" Theme. What episode is that and what is the first song? I can't remember if the scene occurs at the very beginning or the end credits of the episode.