This book is about a traveling young fiddler (female?). She encounters friendly fairies, plays better and better, goes to different venues, sometimes ends up in another realm. I read it in the late 1990s, but it could be older than that. Beautifully and whimsically written. Probably YA.
I don’t know the specific book, but could it be one by Patricia Lynch? Fiddlers, fairies and a sort of ‘magical realism’ are common to many of her books.