I've always been a little leery of books that use music as a major plot point. There are many things that I believe books are best for, but the truth is, you can't necessarily hear the music being described when an author goes on about the fiddler or the flautist. Now, having said that, I think Jane Yolen and Adam Stemple to an admirable job with their Rock'n'roll Fairy Tales, the second of which is Trollbridge. Although the two books are thematically connected, there's no plot line that carries over (that I recalled having read the first one long ago) that you would need to know from the first book to pick up the second one.
The story is its own creation, but takes elements of The 12 Dancing Princesses and The Three Billy Goats Gruff and blends them in a unique and remarkable way. I found it highly satisfying and I definitely recommend it, especially to those of us who enjoy a mix of several tales into one story.
Anyone who's already read this--I'm wondering about the butter carving tradition... any insight into where that may stem from? There's always the reverse, the changeling baby left for the human parents, but I wonder if there's anything in folklore that they borrowed from for the whole butter princess thing.