I saw a trailer for a film, a Vietnam era movie about the music of the 60's, what was it called?

Yesterday, I saw a movie at the second run theatre, so the trailers are sometimes old. It was a movie that was released in Dec 06 but never played in my town. So the movie might have already been to the theatres and left. The trailer was about the music of the 60's and the changing times, it look wonderful, but I've never heard of the movie or seen the trailer before. Can't remember the name was wan't able to find it using yahoo search. Thanks in advance