I have looked, the few tutorials that I have found are even more confusing to me. this guy made it work with this circuit, and his code is there for me to use
Music contains many simultaneous frequencies.
This whole thing harkens back to the days of the Color Organ of the 70's and 80's
Cough cough.I was making theses in the mid 60s. And on the way "invented" opto isolators to control mains lights with the filter outputs, using flashlight bulbs and light dependant resistors in a light proof tube.And also we had the output of filters driving solenoids that moved a lens in the light path.