Hi, I like the concept and the presets are very nice.
Sound : I find a huge difference in sound and CPU consomption when changing the quality. At the best quality, there is still a lot of aliasing when using sawtooth and other waves. Maybe some work to do there. Almost unusable in some cases.
GUI : Buttons are very small and you shoul improve the contrasts between buttons and the fill. Also the dialog which asks you if you want to save your preset is very annoying.
I would like the ability to reset buttons to zero with the left mouse or double click. This dimming GUI is distrating, almost like having a bulb in front of you.
Your envelopes gui is a bit small but otherwise I like it a lot.