Musical vs. Movie That Features Music: My Massive Categorizing Problem

All this got started when someone I follow in Twitter asked the question: what are the three best musical films ever made?

After due consideration, I put down Fiddler on the Roof, Sweeney Todd: The Demon Barber of Fleet Street, and O Brother, Where Art Thou? as my answers. Almost immediately, I had the thought that I much prefer Inside Llewyn Davis to O Brother—it's my favorite Coen Bros movie and in my top ten films of all time—shouldn't it be my third answer instead? But upon further reflection I realized I don't consider Inside Llewyn Davis to be a musical in the same way I think O Brother Where Art Thou? is.

This has had me puzzling for the last day trying to figure out—what is the difference between a musical and a film with a lot of music in it? (Spoilers for both O Brother and Llewyn Davis below.)

My first thought was that O Brother, Where Art Thou? contains music that isn't motivated by anything—the sirens' rendition of "Didn't Leave Nobody but the Baby" and the Klan rally's cry of "O Death" to name the two most prominent examples—while every song in Inside Llewyn Davis is accounted for because it's a film about folk singers plying their trade. But then I realized that this distinction really isn't particularly useful, because that's not in fact the case. There are two songs in Inside Llewyn Davis that are played "just because", without the backdrop of a stage show, an audition, or a recording session as justification—Llewyn plays "Green, Green Rocky Road" in the passenger seat of the car he's taking to Chicago, and later plays "The Shoals of Herring" for his aging, institutionalized father. And the two songs I listed as examples of musical numbers without justification in O Brother in fact do have  justifications of sorts—the sirens are, well, sirens, and the Klan would very likely have music as part of its rituals. But for some reason Llewyn Davis feels stubbornly non-musical while O Brother feels stubbornly musical.

That got me thinking about tone. O Brother, Where Art Thou? could be considered a magical realist film depending on one's reading. There's a blind prophet whose predictions turn out to be remarkably accurate, a guitarist who's sold his soul to the devil, and literal sirens to reckon with. Those sirens are shot in such a way that there seems to be something unearthly about them—the genuinely do feel otherworldly, rather than simple con-women looking to get our heroes drunk and steal from them. And while the Klan rally could be based in reality, the way it's staged, both exaggeratedly comic and somehow still intimidating, reeks of fantasy rather than any attempt at a grounded depiction of historical events. Inside Llewyn Davis, on the other hand, is about as grounded as it's possible for a film to be—it throws out allusions to Greek myth same as O Brother, but they're far more subtle and remain allusions rather than any sort of fantastical intrusions on a mundane reality. So, is that it? Does a musical require a tinge of fancy?

But no, I growl to myself, that can't be it either. There are plenty of musicals about the mundane, from Company to West Side Story. And there are plenty of completely grounded musicals that supply a real-world justification (however flimsy) for every single one of their numbers that nevertheless are musicals.

Is it a matter of the songs in O Brother carrying important character beats and information in contrast to Llewyn Davis? Fucking NO, I grimace, because if anything the inverse is true. O Brother Where Art Thou? has pretty much one song that's about informing us as to its singer's relationship to the rest of the world: "Man of Constant Sorrow" and its reprises. It forms the "I Am" song near the opening of the film and the emotional climax near its end. Apart from this, I suppose one could argue that "Big Rock Candy Mountain" forms an "I Want" song as it plays over the opening credits, but most of the rest of the songs featured in the film are for color—they're designed to set the tone for scenes and to communicate how important music is to the world of the film, but not to really reveal much about character.

Inside Llewyn Davis, by contrast, is pretty much nothing but character-building songs. "Hang Me, Oh Hang Me" is the "I Am" number, establishing for us who Llewyn is and what he feels; the LP recording of his "Fare Thee Well" duet with his dead partner Mikey serves as an "I Want" number, showing us what he's lost; "Five Hundred Miles" communicates Jean's character; "The Death of Queen Jane" is a means for Llewyn to express his anguish and uncertainty over having unknowingly fathered one child and preparing to help his ex-girl abort another; and his final "Fare Thee Well" represents an emotional catharsis that the entire film has been building toward. Some assorted numbers aside, the songs are pretty much all character-centric.

So, by that logic, Inside Llewyn Davis is totally a musical, and O Brother, Where Art Thou? kinda isn't.

But it isn't, goddammit, and it most definitely is.

I would leave it alone, but Inside Llewyn Davis isn't the only film like this. Pink Floyd—The Wall, Walk the Line, and Amadeus, to name but a few, are all movies in which music plays a primary part (the only part, in the former) but that I don't feel comfortable dubbing "musicals". Inside Llewyn Davis is just the most frustrating one, as I have no good reason not to call it a musical but I still don't feel as though it belongs under that label.

And so, I'm turning to you guys for help. First of all, am I even right in thinking of O Brother as a musical and/or Llewyn Davis as not a musical? And second, if I am right, what the hell is the distinction that eludes me?