I can figure out left and right by trial and error if I can't find it elsewhere. (Thanks, though.) But I actually had another project where I wanted to do this where I couldn't join the grounds or I'd get this weird crossover between the channels. And now that I'm doing it again, I might as well figure out what I did wrong the first time.

Edit: Supposedly, tip is left and ring is right. I suppose that works out well with Right == Red == Ring.