The characters are super cute and I love the way they have been animated. I definitely think with polish this could be super awesome!
Since others have already pointed out the controls, ill focus on other things I noticed :)) Once you have a lot of instruments following you, they tend to overlap with the enemies and it gets pretty cluttered. since some of them are similar in color, i would suggest adding a way to add clarity. Also it might just be me but there seems to be some kind of scaling issue as I did play in full screen and on chrome as suggested but the text was way too small in most cases.
For the solo left click, i suggest adding some kind of feedback when you use it as sometimes when i left clicked nothing happened and i wasnt really sure why. Im not sure if there's a cooldown or etc.
I strongly think though you have an interesting concept with the music and minigame for the left click going on and i encourage you guys to polish it and keep it up!
Congrats on the game! It def looks like a lot of care and work was put into it! :))