Let's cut to the chase: Annie Hall is light on music. The opening credits are silent; ditto for the end credits. Artie Butler (The Rescuers, Grease 2) is considered the film's composer, but his real gig was accompanying Annie as she carries two classic tunes: "It Had to Be You" and "Seems Like Old Times."
While there may not be a lot of background music in the rest of the flick, these two jazz standards are vital to the story because they're the signposts of Annie's growth as a singer.
When Annie timidly croons "It Had to Be You," that's Annie 1.0. She's not a very poised performer, and the audience basically ignores her. They chat over her, a phone rings off the hook, and afterward, she's convinced she's the worst singer in the whole wide world. Fortunately, her main man Alvy is there to build her back up. She needs it.
Later, when she sings "Seems Like Old Times," we get Annie 2.0. This girl's got it going on. She's confident, she's literally let her hair down, and the audience is transfixed. Encouragement from Alvy? Annie doesn't need it. When hotshot L.A. music producer Tony swings by the bar afterward to compliment her, she takes it in stride—she knows she deserves the praise.
In this respect, these "It Had to Be You" and "Seems Like Old Times" also chart Annie's evolution as an independent person, on stage and off. After her second performance—and her run-in with Tony—it's not long before she has her eyes fixed on Los Angeles. Without set-in-his-ways Alvy.
But let's go back to "Seems Like Old Times" for a second. Annie's rendition of the song is also played behind the montage of scenes from Alvy and Annie's relationship at the end of the movie, when they meet for lunch, having been long broken up.
As if that song and its lyrics about "staying up all hours" and "doing the things we used to do" weren't enough of an emotional gut-punch, the fact that it's Annie's warm, intimate version in our ear-holes ratchets the poignancy of the montage up 100%. With that song choice, things get personal.