The Pitch of each oscillator is determined by corresponding potentiometers and the three switches between the oscillators open up light-sensitive connections between adjacent pots. This means both oscillators’ pitches will bend according to the amount of light the photocells receive (LED’s indicate strength of current flowing between the pots) The Tone pot controls a shelf EQ on the master output, with cutoff frequency at 482 HZ and the dangling LED is there for you to use to play the light-sensitive circuit. Adjust the brightness of the LED with the pot next to it. DRONE/KEYS switch chooses between either all 6 voices playing constantly or voices playing only when activated with key. Use 9V center positive PSU.