IThis is classic… This is the program on PBS I saw and I recorded when I was 15, and subsequently began playing the fiddle. It’s funny to see 20 years later and I can play all the tunes in my own style. Everything I thought was so difficult in the beginning. Time flies.
I don't think it's to get stereo sound. I think an output goes to a multi-effects and with an octave allows him to get the bass, but i'm not sure either. (Sorry for my bad English in these technical subjects) Greetings from Spain😃
Another commenter said he probably has one output for a piezo type pickup and one for a microphone mounted inside the guitar. That seems likely to me; I think the low sounding note is just his lowest string (D; he is not using standard tuning) however with the use of the microphone and mixing board that note sounds louder and more "boomy" than it naturally would.
