I think in this case you'd be signed to do the soundtrack album - and have a single on that. Usually the ST is distributed by a major distributor or large independent - depends on the film.

Ever wonder why some songs are in the movie but not on the soundtrack album? The movie cats may get a master use license for film but not a duplication license so therefor it can't go onto the ST album :) In some other cases, the ST album distributor may cut the song for continuity reasons too - politics. But usually it's the first reason. An artist is already signed and the owning label doesn't want the song out on a competing label.

If you are accepted into the soundtrack and you and your publisher agree to the use on the soundtrack album and you don't have a major label deal, or an indy for that matter, you may be signed for that one song. However, if that song is a feature song, or on the end credits or something (that's a good place to be!) the distributing label may release it as a single. Then you could get signed by the dist. label or noticed by another. If you get your song on the ST in a major motion picture, good on you! It could be a springboard and most definitely a negotiating point.

D