The most blatant use of music in a "romantic" context, by which I mean a sexual context, might have been the use of Ravel's Bolero in the movie "10" to accompany a liason between Bo Derek and Dudley Moore:
As I recall, that wasn't very successful. A scene in Buffy the Vampire Slayer where Willow is attempting to seduce Oz is accompanied by Barry White:
For classical music buskers, who try to create a romantic vibe, the three big tunes are the Adagio from the Concierto de Aranjuez by Rodrigo:
The Romance anonimo for solo guitar:
And possibly Memory from Cats by Andrew Lloyd Weber:
Another good one, if you are a flute player, is the Dance of the Blessed Spirits from Orfeo ed Euridice by Gluck:
So tell me, what is your favorite romantic music?