If someone is not specifically commissioned the soundtrack of a movie would be composed by the musical director.
Hans Zimmer .
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.
is an Australian composer, classically trained musician, singer and songwriter, renowned for her role as the violinist of the band The Go-Betweens and more recently a session musician and soundtrack composer.