A few days ago a had the pleasure of seeing Michael League perform with Bobby Sparks and they sure tore it up. Michael was playing a P bass and I was sure plugged in to an octave pedal. I asked him after his set what pedals he was using, he said he wasn't using any pedals but a technique when fretting in around the third fret you can get undertones. He tried to explain it to me but I didn't get it. Any input how this works?