I remember an animated movie I watched as a kid. it involved a boy befriending some sort of mischievous music not imp creature but then it started convincing him to skip the things he needs to do to have fun. and i beleive he turned into or summoned a big demon near the end.
okay so i found out what it was it was called ” Journey through Fairyland” it does not look great but I found better movies along the way and im still curious enough to watch it again sometime probably on youtube i guess
Glad you found it and thanks for letting us know dustinb!
sure thing