My sister told me about this one. I remember vaguely about it but I can't remember many details.

A young boy has to save his father the king. He has a (gold?) cape which makes him invisible, and some kind of musical flute?) That is all we can remember. Sorry. Thanks!:)

I don't know If this helps but here goes :) When I was little we used to watch a movie called "Long Ago and Far Away" where the young buy lived with his aunt who didn't love him (and for some reason) ends up traveling to see his father who is a prince or something... not much But I hoped it helped :)

Thanks for your help. I don't think that is it exactly but I may have found it elswhere. I think the movie I am looking for is called Mio in the land of Faraway. Thanks again.