I play twelve string and tuning is very important.

FIRST - tune the 12 strings with your electronic tuner - I can do it by ear but on stage, in a rush, noisey environment and ACCURACY. Get the whole lot spot on.

SECOND - detune one of each pair slightly2 or 3 cents MAX. The best test is your ear - if it's quiet enough.

THIRD - listen to the resonances created by the slight off tuning of the pairs - think of the resonance of two violins rather than one. Think of synthesizers to get a good sound out of a Moog you always had to detune one oscillator slightly.

FOURTH - if you are getting technical, then talm to a piano tuner about "beating notes." On a piano the sets of treble strings need to be in tune - but the skill of a good tuner is to create just the right amount of detuning to give the sound more life.

Hope this is useful.

Bruce