First of all, lemme enjoy my 2nd place on the score board for a second haha. My comment would be pretty bias since I've play tested your game during development on discord so I already knew the rule and all haha. The game did get a lot more interesting around level 10 and higher, and I was able to exploit a bug that was super helpful (and I think you should keep it as an intended feature): if I place a note right when the tracker comes to a column, it would automatically registers as a correct note. If it doesn't, I know it is not the correct note and I toggle it off before the tracker hits it in the next loop and spawns a spider. I was very happy with the score but then I committed suicide because later levels are just not as rewarding. At the moment, I earn very little score when passing levels from 15 beyond, because it takes just about 100 moves to solve the puzzle (it took me about 80 each level given the fact that I was exploiting the bug). In order to maintain the satisfaction after handling a hard puzzle, there should be a reward chest for completing the level after each ends, whose value increases every level. That way, you can tweak the increment in reward accordingly to the level of difficulty. Increasing the number of moves to start with could be a solution too, but that prolongs the game and would make players not planning carefully for their moves.
On the good side, I think your game has every element of a fun game, really looking forward to seeing further development on it such as more enemies like you said, or even a local coop mode to play with friends, if someone has. Good job!