Continuity mistake: When George is in the boardroom, he places his briefcase on the conference table, and opens it, with the top leaning against a carafe. As George yammers on, the briefcase is closed in a couple of shots, and then open again for the rest of the scene.
Continuity mistake: In the episode 'The Soul Mate,' there is a scene where Kramer is talking to Jerry's girlfriend in The Library with the help of Newman. Kramer elbows Newman through the shelf knocking some books down, but in the next shot we see Newman rising and the books are back on the shelf.
Continuity mistake: George has constructed a model of the boardroom when his briefcase was destroyed. Jerry thinks George should be represented by the Yellow M&M figure. When the camera shows a close up of the figure, Jerry is holding it in a different position than the far away shots.
Answer: Composer Jonathan Wolff used a synthesizer, although in seasons 7-9, a real bass is used in addition. Wolff also recorded himself making hundreds of mouth noises, pops, and slaps to add to the synthesized bass licks so that each episode has a different theme. The only real "back-story" is Jerry Seinfeld was having trouble coming up with a theme song and talked to a friend who happened to know Wolff. They wanted to avoid that cheesy late 80's sit-com theme song and Wolff came up with what we enjoy now. Jonathan Wolff has also talked about this further in interviews, recently Reed Dunela interviewed him, so for a fuller account of his story; check out "The Wolff of 116th street".
Bishop73