Comment by techie2022

Tapping the keys at a certain frequency is the same thing as PWM control, which gives you an duty-cycle-based analog-like control input. PWM is just on_time/(on_time + off_time), so there are a number of ways to do this even with the key input as you have it. Again, in summary: you can do PWM duty-cycle control or tap-frequency-control, which is really just the same thing.