Continuity mistake: When Elaine and Jerry are confronting Testicoff about paying for the woman's hospital bill, in the view from behind Testicoff he puts his left hand down to scratch his pants. When the shot switches to a closeup of Testicoff, he is waving both arms above his head.
Continuity mistake: While George is telling the whale story in the coffee shop, the ketchup bottle on the table disappears and reappears between shots. (00:19:00)
Continuity mistake: When Elaine is on the phone in Jerry's apartment, she holds the phone with one hand and lets the phone cord hang straight in one shot, and in the next shot she has the cord bunched up in her hand. (00:00:50)
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