When Vidal talks Jean-Louis into going to a concert, "to meet girls,"
they are shown listening to a generous portion of a violin and piano
concerto that is the theme music on the Criterion DVD. I had never
paid much attention to this before, but I fell in love with this piece
and had a bit of trouble locating it, since it was not identified in
the credits. IMDB lists the name of the violinist as Leonide Kogan but
provides no further information about the music. Finally, I located it
on YouTube of all places searching Kogan and the film title. This
confirmed my first guess that the composer was Mozart. Here's the
link:
http://www.youtube.com/watch?v=utlN41x2Fv4