well, I tune it when I hear something wrong, but my ears are not the best...

Once, at Winfield Kansas, Li'l Roy Lewis, of the Lewis Family, saw me carrying my 'harp, and because he plays one, asked to try my (then new) 21 bar...he strummed a chord..wrinkled his brow and said "something's out....you got the 'krenk'?"..(crank..as in tuning wrench)*grin*...then he proceeded to fix it in a couple of deft twists! What I would give to HEAR like that!..He simply KNEW what note was wrong in a whole bunch.

I use a Korg, and it makes life a lot easier....but Bryan Bowers once told me he could not use an electronic tuner, because he felt that 'perfect' tuning was not right...he claimed that not only do you need to tune string 'x' differently for different keys.., but the whole thing needs to be 'slightly' sharp at the lowed end and flat at the higher end!...So he tuned entirely by ear and used those mulitple 'harps to make every key sound balanced.