Discovery Lullaby by Jeff Russo

In one of my favorite episodes of Star Trek: Discovery season 3, Adira reveals that they are carrying the symbiont of their former boyfriend Gray. This news brings the crew to Trill where, after an initially hostile reception, Adira is permitted to enter the sacred pools in the Caves of Mak'ala upon which they are reunited with all of the Tal symbiont's previous hosts—Gray included.

The episode concludes with Adira picking up a cello, an instrument that we previously saw Gray play during a flashback. As they play a melody, which later turns out to have more far-reaching implications that we expect, Gray appears to them, critiquing their bowing technique.

I'm honestly a sucker for cello in general, and high-register cello in particular. The melody Jeff Russo writes for this moment is absolutely gorgeous, and while I don't think the galaxy-wide reach of this melody is every really satisfactorily dealt with, its use in this scene is wonderfully affecting.