For Sherlock, The Sound of Pulling Heaven Down by Blue October. (For Jim and Sherlock, there's a playlist, because of course there is.)

For Steve, the Mountain Goats's Sax Rohmer #1. For Steve and Bucky, I And Love And You by the Avett Brothers (AKA "Brooklyn, Brooklyn take me in")

I don't have anything for Dirk Gently yet, but I would bet if he did fall in love his song would be something very sweet like Oh by the Dave Matthews Band.

I also think Sit Down by James would suit a lot of patrons, with its theme of "If you're a misfit, let's be misfits together."

All links to Spotify.