Think of the last movie you saw. During the romantic Crowning Moment of Heartwarming, there was probably a sweet, soft song in the background. That "song" would be this trope. In real life, couples try to come up with "that one special song" that represents their relationship. It's no different than in fiction. Often, a main couple in a fiction work will have a song about the two of them, and their relationship. These can be found in films, television and even anime. This song might also be playing in their Falling in Love Montage Another thing to note-many, many love theme songs will become an Award Bait Song.