1) Songs are able to express things that dialogue can’t
Words that are sung contain a certain power, one that, like any other power, can be used for good or for ill, and sometimes some combination of the two.
Roger Ebert liked to write about this. In some cases, singing words can turn them from ridiculous nonsense to charming sentiment. The best uses of song in movies allow dialogue to have an amount of poetry that rivals the celebrated rhythm-based dialogue of people like Quentin Tarantino or Aaron Sorkin.
I think this is because in the same way the use of scored music in basically every movie we watch is designed to influence our emotional response to the images we’re seeing, movies that are even more deeply based on musical sensibilities tap our emotions in an even more affecting way. It makes the cinematic imperative for these films emotional truth, a source of feelings that resonate rather than sustaining ideas or impressions. I find contemporary musicals draw on this far more effectively—or else they’re just more geared towards audiences of my generation. I think of Tim Burton’s Sweeney Todd or something as seemingly slight as Hairspray as two unexpectedly affecting movies that I was initially resistant toward before being swept up in their contrasting tones.
Emotions tend to get treated with less respect in art than thoughts, but it’s just as important that movies skillfully make us feel as it is for them to provoke thought or inspire awe.
