So I'm seeing Rock'N'Roll High School tonight, which appears to be a single artist musical, based around the Ramones. I don't have high hopes for it, and not just because the director's last movie was Caddyshack II nor cuz I'm not all that fond of The Ramones (the only thing I can remember about them is that one Simpsons bit and that they had a song on Rock Band I was not fond of playing).
No it's because single artist musicals based on pre-existing music tend to be not good. Even the best, in movie form (Across the Universe, if you're wondering) is not exceptional, it's merely better than the rest, and given that it's primary company consists of Mama Mia and the Sgt. Pepper's Lonely Hearts Club Band movie means that being the best is not fucking hard.
See, in most musicals all the songs from the silly (Until Tomorrow Night from Smile, Somewhere That's Green from Little Shop of Horrors) to the romantic (Chanson from The Baker's Wife, Defying Gravity from Wicked and don't you tell me it's not a romantic song) to the deadly serious (Castle on a Cloud from Les Miserables, Joanna from Sweeney Todd) don't only entertain and excite us, but also move the plot forward and help characterize the characters (I hate the last part of that sentence).
But when the songs are pre-existing, either the plot has to be built around the songs (difficult) or they have to cut away from the plot for these little 3-5 minute digressions, which means every time it happens the plot gets shorter and shorter. And what's really annoying is they never do it based on an album that has a story, that isn't already a Rock Opera or Show (Tommy, The Wall).
There are plenty of albums with stories you could movies or musicals around. Arthur or, the Decline and Fall of the British Empire by The Kinks comes to mind, if you want something dry and humorous. Want something bigger and more fantastical? Why now The Rise and Fall of Ziggy Stardust and the Spiders From Mars by David Bowie. Hell, Coheed and Cambria supposedly has a lengthy overarching story going on in the background of their entire musical career, you can't tell me you can't hammer a working narrative out of that (Example? 10 Speeds (of God's Blood and Burial) is about what amounts to Luke Skywalker talking to his evil Bicycle. No really.)
Just some food for thought. Dunno where, if anywhere I was goin with it. Still, if a movie producer is reading this, go look up the story to Ziggy Stardust and then tell me that wouldn't make an awesome movie.