guitars in mono!!!?? what about using an XY pattern on guitars!!!??? UH OH!
lol, i'm just kidding you
guitars are sometimes recorded in stereo (ie. two microphones). One on the twelfth fret and the other on the tone hole.....if we're talkin' acoustic guitar. kinda like farview said...the way i see it is if the instrument produces two different sounds in two different places, then you try and record those places. Usually these instruments will also be two different sounds in the totally OPPOSITE places. Like in guitar....one on the neck and one on the body. On piano, one on the lower strings, one on the higher ones....on drums, one on each cymbal or each side of the set.