Yeah, good one. The credits thank The B-52's* at the end. The Zevon case is illustrative. There are situations where filmmakers don't like a commissioned song and drop it from the cut and the musician releases it anyhow, and even produces a video without footage from the film, which is the big advantage of such songs. Two I can recall are "Romancing the Stone" (in which only a few instrumental bars of Eddie Grant's failed title song appear, and Crosby, Stills, & Nash's "Wargames," which ended up on the cutting room floor of the film that it was commissioned for. *In 2008, the band long known as The B-52's dropped the apostrophe and now refer to themselves as The B-52s.