tune to the same octave, but eqed to have a complimentary sound, usually in the mids if they are super scooped. In fact, if they are silly scooped and you do it right, you can comletely vanish the guitars which is satisfying. Otherwise Heavy strings and bridge pickup, so you have the low tuning but plenty of harmonics to give some audible. A high pass might be good to not waste power on speaker flap.