...if you're a luthier, that is.
I was wondering why a Yamaha classical guitar I purchased a few years ago always seems out of tune, and started a discussion about it in a guitar forum, including measuring the pitch while each string is open and fingered on the 5th and 12th frets (bizarrely inconsistent results). They suggested I check out this fascinating article by Gregory Byers. It describes the lengths (pun not intended but allowed) a guitar-maker has to go to to create a situation where each string is somewhat in tune on each fret. My Yamaha was not made that carefully! Of course very few guitars are. Byers spends a month making a guitar, and they cost $9,500.