(Play a few chords when opening again after a break?
It seems to have been adopted by quite a few TV shows after Seinfeld.
Welcome Back Kotter would play the opening notes of its theme all the time during act breaks etc.
The Bob Newhart show did it.
Can you give us some recent(since 1998) examples aside from the famous Seinfeld one?
Taxi and Brady Bunch both did this.
It was done in sitcoms as far back as the 50s.
I believe Gilligan’s Island also has these.
This is so incredibly common, I can’t imagine how anyone would think Seinfeld was the first.