Interesting concept, I like the idea of a musical puzzle a lot.
However, I feel like something in the core mechanics should be changed. I find difficult to tune intruments, I always hit one by accident and lost my note. This make the puzzles much harder to play in the wrong way, I know what to do but I'm struggling to do it. The best example of this it's the level full of harps (level 12), I can never tune the harp I want, and if I came to the wrong angle I get launched miles away. Once I also get trapped in a loop, looking the poor Tonic be a pinball ball for quite some times (it was pretty hilarious, though XD).
In my opinion, another thing that can be improved is that the game is full of noise. Both literally and metaphorically.
Literally because all the sounds made by the game elements don't blend well with the background music. After a while, it becomes rather annoying.
And metaphorically because the level desing is full of stuff, somtimes that's not helpfull to solve the puzzle at all. I may suggest to reduce the number of game element in a single level. I play the game to the end and some levels were cool btw, I had fun playing them. Some others were a bit frustrating, like levels 12 and 13 for example.
Aesthetically, I really liked the game. The art style is pretty cute and the character is well designed.
Overall I had fun playing your game! I think the concept is very interesting and there is room for improvement ^^