I love the art style here, the cute monkey and his Whiplash style instructor mercilessly hanging over him. Creative theme interpretation to make it about climbing the guitar scale.
However, I gotta say, it is very difficult with the punishing fail scenario of a few missed notes, I admit I could not get through one song. I'd suggest letting a player flail around for a bit and have the chance to get accustomed to the game without kicking them to the main menu, maybe with a percentage score at the end of the scale and an angry, disappointed, satisfied or beaming teacher at the end, accordingly.
All in all, love the creativity and keep going with your artwork!