Hmm..
I have a flute as an item. As Udgard said, It would be wonderful if the item could be used to cast spells with the help of principles. For instance, I would love it if my flute could use heat and based on my principles give healing or increased attack depending upon the type of music played. For instance, a strong, fast music would give attack which can be explained as giving the character a sense of morale boost for war, or calm soothing music which gives relaxation, peace and healing. But What if, like, the number of times I play a tune on my flute, meaning the number of times I cast the spell, would give me more experience playing the tune and I would learn to cast it better, Like about every 50 times I use the spell, the level increases by one. Of course, that would mean that the number of times I would use my flute for magic would be reduced to like 3-5 times in two weeks? I dunno.. I was just guessing...