If there's one song on your playlist that always brings tears to your eyes, maybe it's because it has an elegiac quality. Elegiac means "mournful or sad."
The adjective elegiac is useful when you're talking about music, a movie, a book, or another work of art that has a sorrowful tone. Sometimes elegiac specifically refers to something or someone that's gone: a person who's died, or a time in the past, especially if you feel a sense of longing for it. You can speak in an elegiac way, or sing an elegiac tune. The word comes from the Greek elegos, "poem or song of lament."