Adam Fields - Stardancer 

This is one of my favorite scores from the series. It's a beautiful piece and always gets me teary-eyed.
It was featured in the fourth season and was included on the score album.
It plays at two points that I know of, between Joey and Pacey after her Worthington party (4x09) and again in the Witter basement when Gretchen tells Dawson and the kids about "Stardancer", the name of the piece (4x12).
This piece seems to be about Gretchen coming back to Capeside and not being able to stay, sort of foreshadows the season. However, it does plays in that sweet moment between Joey and Pacey as well.
Enjoy! :)