It has come to my attention that some folks are looking for a theme that connects all four jams - there isn’t one

Per the OP:
“each jam is connected to the next by a theme; you don't need to identify the themes to win, and the themes only connect consecutive jams (not all four)”

In other words: there is a theme that connects the first jam to the second, the second jam to the third, and the third jam to the fourth; but those are different themes!

By way of example:
1) 12/30/19 Tweezer
2) 12/30/99 Mike’s Song
3) 11/14/95 Stash
4) 8/28/93 Stash

1-2: 12/30 jams
2-3: Florida jams
3-4: Stash jams

P.S. we have our first correct answer!