Hi Everyone, i need some help to find a old cartoon with a specific wonderful flute melody that has mentaly imprinted my memory and it pains me that i can´t remember the name of the cartoon so i could look for it.

it was from somewhere in the east of Europe, i remember it was a boy or man who got a special magic flute from a black gnome to win the heart of a nymth or something and gets in forbidden love and seperates, later they try to find each other and the boy gets help from a dark gnome and transform into a bat looking guy and flies to the island while the nymph has to give up her immortality and gets sended to the human world but gets captured by a sheriff/knight (the villinan) and they dont find each other until the boy join a knight tournament to win the princess (nymph) and after the tournament she dont belive it´s him until he plays the flute again and turns him normal again and they live happily ever after.

that´s all i remember

i really really hope you can help me finding the name of that animation