(Ooh, interesting. Watch me ignore my NaNo to leave you an intelligent comment for Doc.)

I don't really have a playlist written out for him but it involves music more for mood than anything. A lot of Tom Petty. Almost all of Highway Companion is a given.

Saving Grace is a definite one.
Flirting With Time is probably my Doc/Billy song for how he feels about it all.

Johnny Cash works, sometimes. Bon Jovi works for the more badass moments, but hey it is a 'bratpack Western'.