Today I watched two great old movies back to back: To Have and Have Not and Night of the Hunter. Each film effectively worked in live performances of music - with the characters singing in an otherwise nonmusical film - to enhance the story, the tone, the plot. This is a device that has been used to great effect in a number of films, including many by Robert Altman, Tender Mercies, O Brother Where Art Thou, but how often has it been done successfully using a rock song or rock songs? I'm not talking about rock soundtracks of the Martin Scorcese/Wes Anderson variety. I guess that long, excruciating cover a Van Morrison by Jennifer Jason Leigh's character in Georgia is close to an example, but her character is a rock musician. Is there a movie in which a character simply picks up a guitar and bangs out a song? Will Ferrell does, come to think of it, in his "serious" film from the past year, when he plays "Whole Wide World". Any other examples that are that casually woven into the plot?