“The Leftovers” is not only the best thing to watch on TV right now, but it’s also the best thing to listen to.

The HBO series — a semi-apocalyptic drama about the aftermath of the Sudden Departure, in which 2 percent of the world’s population disappears — defies easy classification. It’s mournful and mordantly funny, absurdist but dedicated to the search for meaning. And it captures this ambitious mix of tones and contradictions with the most imaginative soundtrack on the air.

This is the sort of show that imagines the afterlife, in the second season finale, as a grotty karaoke bar in which Kevin Garvey (Justin Theroux) performs a shaky rendition of “Homeward Bound” while hovering between life and death.