Hans Zimmer .
If someone is not specifically commissioned the soundtrack of a movie would be composed by the musical director.
Danny Elfman
Composer Jesper Kyd, famous for doing the soundtrack of the Hitman series of games.
For my opinion:Hans ZimmerRandy NewmanJohn Williams
Composer Michael Giacchino .
This film and soundtrack are both available on iTunes. The film is in the short films section, and the soundtrack is on the composer, Felix Brenner's page.
The cast of Soundtrack of Her Life - 2013 includes: Johanna Lavender Max Pettit as The Composer
If you mean the British TV show, then the composer is Warren Bennett.
James Horner is a music composer. Most notably for the titanic movie soundtrack.
Oingo Boingo
The pianist and composer Lionel Cole performed the soundtrack for the film Asunder.
Many soundtracks aren't in the order of their movie. It would actually be bad to have "Inception" in the right order because the tracks sounding similar (Dream is Collapsing, Dream Within A Dream, etc.) would be playing for a long time and "Time" would be spread out all over the soundtrack like little bits of it are in the film.