The story takes place in a small village that has banned technology and musical instruments. We only hear a bit about the outside world when he eavesdrops on his parents.
The protagonist also hears that he's not his parents' son; he's a clone of "dad's" former colleague, an outstanding scientist, but he doesn't understand what that means.
Outside of the village there's wasteland and some form of monsters, possibly mutants. His childhood friend (girl) gets taken to their cave, and has a monster baby after they take her back.
They salvage an organ, and he becomes really good at playing it. But he plays some angry tunes at some point, and he is quarantined in the cottage overlooking the village. Then he sees them burn the organ, and he kills his brother, the real son of his "parents" in his rage. Then he runs away, book ends.
I think the author was Danish. I read a translated version in norwegian, but don't know if it was ever translated to English. It was supposed to be a series AFAIK, but I only read the first one. It was probably published between 2006-2010. Help would be greatly appreciated!
Update: There's about a dozen boxes full of books in my parents' basement, and we've scheduled to go through them within the next week or so, as they need to get rid of some of it. One of the Game of Thrones-books was there, so perhaps I'll find it eventually.