Since I have not heard all of the Music which has been written past, present & future, I could not speculate upon a specific piece of Music.    The sexiest work of Music I have heard, is another category entirely--I'd have to boil it down to a tie.
   When I was in college, a certain boyfriend of mine was passionate about JS Bach. We were listening to the Brandenburg Concerto #2, when he pulled me close & I said, "If you'll do the figured bass, I'll do the piccolo trumpet."
And then there's . . .
   Some years back, I was with a friend who said she had to stop off at the family business to pick something up. She said, "Come on in with me--you'll find this amusing." We went in through the back door, & down the hall from the office was a large room where there were Musicians playing Indian instruments--Sitars, flute, tablas & such. I'd heard ragas before, but nothing like that. She told me it was Classical Indian Music specifically composed for the art of making love. The family business was a brothel.