how do i find the information to compare and contrast the music from the movies

It might help to know which movies you are considering.

http://www.jiskha.com/display.cgi?id=1275313285

My best suggestion is to listen to the soundtracks several/many times and take notes:
http://www.google.com/search?q=%22parent+trap%22+music&ie=utf-8&oe=utf-8&aq=t&client=firefox-a&rlz=1R1GGLL_en___US379
and
http://www.google.com/search?hl=en&client=firefox-a&hs=CbT&rlz=1R1GGLL_en___US379&q=%22sound+of+music%22+music&aq=f&aqi=g-c1g2g-c2g4g-c1&aql=&oq=&gs_rfai=

To find information to compare and contrast the music from movies, you can follow these steps:

1. Movies Soundtracks: Start by identifying the specific movies whose music you want to compare and contrast. Write down the names of these movies for reference.

2. Online Resources: Utilize online platforms like IMDb (www.imdb.com) or AllMusic (www.allmusic.com) to gather information about the movies' soundtracks. These websites provide comprehensive details about movie soundtracks, including composers, song titles, and any notable musical elements.

3. Film Reviews and Analysis: Look for professional film reviews or analysis articles that discuss the music of the movies you're interested in comparing. Websites like Rotten Tomatoes (www.rottentomatoes.com), RogerEbert.com (www.rogerebert.com), or reputable film-oriented blogs can provide valuable insights and critical perspectives on the movies' musical aspects.

4. Official Websites and Behind-the-Scenes Material: Visit the official websites of the movies, if available, to explore any behind-the-scenes content or production notes. These sources often provide in-depth information about the scoring process, music choices, and collaborations with composers.

5. Composer Interviews and Soundtrack Commentaries: Seek out interviews, podcasts, or YouTube videos featuring the composers or musicians associated with the movies' soundtracks. They often share their creative process, influences, and intentions, which can assist in comparing and contrasting the music.

6. Music Analysis and Theory Books: Consult books on film music analysis or film soundtracks to gain a deeper understanding of musical techniques, themes, and motifs commonly used in movies. Books written by musicologists or film scholars can provide valuable insights.

7. Online Communities and Forums: Engage in discussions on forums such as Reddit's r/movies or dedicated movie/music communities to exchange thoughts and gather recommendations from individuals with similar interests. These communities can provide diverse perspectives and suggest other movies with comparable music.

By combining these steps, you should be able to gather ample information to compare and contrast the music from movies effectively. Remember to take notes and critically evaluate the different musical elements that you discover to make your comparisons insightful.