The Way Back (http://rainylemons.livejournal.com/29425.html) is a long AU fic that has guitarist!Dean at the end.

Wow! That was quick.
Thank you so much! I'm so excited to read it!

How about these Dean/Cas fics?

Shootin' You Straight (http://rockstarpeach.livejournal.com/96787.html) by RockStarPeach
Word count: ~40,400
Summary: AU. Dean Winchester is in a rock band and Castiel is a fan. Not of the music, of Dean. An opportunity presents itself one night after a concert and Castiel can’t pass up the chance of a lifetime. It's not perfect, but this is their story.

A Place Only You Can Go (http://archiveofourown.org/works/539573?view_adult=true) by iamthemagics
Word Count: 25,000
Summary: Castiel Singer has been living with cardiomyopathy since he was fourteen. He lives with his adoptive parent and sister. While gearing up for graduation ( his sister and lifelong friend Sam), his heart starts to decline. He tries to work through the pain the best he can until his boyfriend, Dean ( a fledgling musician) returns home for a tour. But after an'episode' that lands him in the hospital, Castiel and his family discover that he is in need of a transplant. Castiel has to step back and consider his relationship with Dean ( who sleeps with others man and women on tour and Castiel is aware) and the guilt of causing financial crisis to his family.

Thank you! These sound great; Ooo, the second one sounds stomach twisting and awesome.
You made my day :)

Come On with the Rain (http://archiveofourown.org/works/568714) has a bit of Dean guitaring and singing in it :)

I believe that Lakota Falls (http://anne-higgins.livejournal.com/24798.html) by Anne Higgins has some Dean singing and playing guitar in it.

Hope you enjoy!