Love the instrument! You've got an oscilloscope, FFT, and Lissajous figures all in one game! Such a nice touch for the Signals theme. I never realized this was something I needed in my own game haha. Love your interpretation of the theme, the art, and the game overall. The soundtrack and sound effects are really nice too!
One thing I'd suggest, if you don't mind, is making the controls a bit clearer. Maybe adding more visual feedback when interacting with buttons, like changing the cursor or highlighting them with an outline, would help a lot. Not all buttons are interactable, which can be a little confusing at first. Other than that, really nice work!