Continuity mistake: Kramer's moussed up hair looks much different in the first shot compared to the rest of the scene; it's way slicker and frizzles up right after the first cut. (00:00:55)
Continuity mistake: When Jerry's neighbours are arguing in the corridor about sponge size, Harold is holding the tiny scourer in different ways between shot (in a different spot and with his fingers suddenly stretched out). (00:08:40)
Continuity mistake: At Monk's, Jerry points at the woman feeding corned beef hash to her baby. There's an angle with the camera roughly behind Jerry Seinfeld's shoulder; the continuity here is sloppy, with George having his hand down flat on the table instead of with the fingers laced together with the other, and he has his right leg crossed and not the left. Just few seconds later he asks Jerry if he remembers his friend from Detroit, and he is pointing his left index finger at Jerry across the table instead, again, of having his hands close together. (00:07:30)
Other mistake: Jerry is at the party Elaine's friends have during the marathon. The clock in their living room never changes the displayed hour. (00:15:20 - 00:18:50)
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