New York, New York
This is a challenging catagory so I'll get it out of the way while I can with my first choice.
I love this movie but it was not a financial or critical success. In fact it drove director Martin Scorcese to depression and drugs due to its lack of success.
Liza Minelli is a singer and Robert DeNiro is a saxaphone player. All of the music in this movie is part of the story as they perform and audition and the music is tremendous. If you like big band, jazz and 40's music you should enjoy the soundtrack. It is the only soundtrack I have in regular rotation on my ipod.
As the war (WWII) ends they meet at an audition, eventually join the same band, marry, seperate, have a kid, but always follow their music.
Animal House (Sutherland)
New York, New York (realistic musical)