This is the only thread that I can find about the PB-300. Does anyone know what kind of signal is the “Bass Note”? the one that goes to R13 (22K). I breadboarded the circuit and feed R13 with a PWM from an Arduino (0-5v). I get a light bass drum sound on the bottom and a sound like a bell on top, if that makes sense. While I was playing with the circuit, I leave a floating wire connected to R13 and the bass sound appeared. The sound changes as I move my hand around the wire. My only reference is a guy playing with a keyboard and the PB-300 on youtube, and the sound is pretty much the same on the video. I will appreciate any help.