Others have given some good recommendations, particularly the Scarborough novels. For myself, I find Sharyn McCrumb's writing uneven (some of her mysteries I've liked, but Bimbos of the Death Sun is at best a highly problematic portrayal of science fiction/gaming fandom, which is its primary focus).

I'd echo and amplify the mention upstream of Manly Wade Wellman's series about John the Balladeer, aka "Silver John", which is probably close to being as definitive a treatment of the traveling folkie's life as you'll find under the fantasy genre's umbrella.

That said, a handful of other suggestions:

Emma Bull's War for the Oaks - widely regarded, along with Charles de Lint's early novels, as one of the cornerstone works of modern fantasy - features a central character who's a singer and organizer of bands. The music itself shifts between folk, rock, and the fuzzy zone between, but folklore and folk traditions are deeply woven throughout the novel (and Bull herself has been a singer, part of a duo known as the Flash Girls). Strongly recommended, rock elements or not.

Bedlam's Bard by Mercedes Lackey and Ellen Guon, also involves a core cast including folk musicians, in this case cross-pollinated with SCA-type medieval re-enactors as well as elves. There are a number of sequels (and a couple of other intersecting series), although the level of musicality in the plots fluctuates a good deal over the life of the series. Lackey overall is a more lightweight read than Bull, but she and her various collaborators know the folk traditions very well. (Lackey is also an experienced lyricist; there are a number of albums extant featuring folk music set in her "Heralds of Valdemar" high fantasy universe, on which she is the primary writer.)

Singer of Souls is by Adam Stemple, who's likely better known in Mudcat circles as part of Boiled In Lead and/or the Tim Malloys. If that's not a persuasive credential for a novel about a folksinger in three kinds of both magical and mundane trouble, consider that he's also the son of Jane Yolen, possibly one of the world's premier writers of folklore and fairy tales for children.