Ok, time to cheat again because I can't just pick one this time...
The Season 3 episode of Star Trek: Picard, "The Bounty," finds us visiting the Starfleet Museum at Athan Prime. While the USS Titan is forced to hide among the starships that have been retired there, Jack Crusher and Seven of Nine spend a moment admiring the ships of old. This provides composer Stephen Barton to dust off not one, not two, but four previous themes.
Throughout the Star Trek: Picard Season 3 score, Barton and Frederik Weidmann do a superb job of quoting both old themes and old styles of music from previous Trek shows and films, and this cue is a perfect illustration of that.
But we aren't done here!
Because if you had asked me to name another theme that I didn't expect to hear again in Trek, especially before the launch of Star Trek: Strange New Worlds, it probably would have been "Archer's Theme" from Star Trek: Enterprise. A theme that had been largely relegated to the closing credits of that show, I suspected that there would never be a reason to bring up it or Jonathan Archer again especially with Discovery having made the leap to the 32nd Century. And yet, in "Kobayashi Maru," the first episode of Season 4, we saw the dedication of the new Archer Spacedock. And of course, Jeff Russo took advantage of the opportunity to bring back his theme. I loved this moment so much that I had to include it as a bonus cheat pick!
Note: the original cue is about 3:20, and since this is a cheat pick, I'm including just the excerpt that includes Archer's Theme.