We often get customers in the repair shop explaining their various forms of “tuning problems.” Surprising to most guitarists, this is rarely due to the tuning machines themselves. True, it is sometimes due to faulty tuners, and a set of high-quality tuning keys will enable better and more accurate tuning of your instrument. But “tuning problems” most often come from how the guitar was strung up at the machine heads. Also, just as common is a guitar with improper geometric relationships between the neck relief, nut height, and saddle height. Fret wear and fret crowning profile (or lack thereof) are sometimes culprits here as well. Essentially, this means your setup is out of wack.
It really helps to have the right number of wraps around the machine heads for each string. When re-stringing your guitar, with each string make sure there’s enough slack so that you get 5 wraps around the machine head for strings 1st – 3rd, and about 3 wraps on the posts for strings 4th-6th. It is also important to bend, or kink the string on both sides of the post hole. After a rough tuning, stretch the strings at each end to set them before fine tuning.
Many tuning issues can be resolved with a proper restringing and some minor adjustments.” -Ryan Elewaut
All three points of the guitar’s setup must be properly adjusted in relationship to one another for a guitar to play properly and in tune, up and down the neck. Some “tuning problems” are described as, “the guitar doesn’t stay in tune when I play up the neck, or when I use a capo.”
The worse off your setup, the more pronounced this phenomenon becomes. Old strings are also more difficult to tune– actually, old strings loose their even-order harmonics and this makes them sound out of tune with each another.
If you have too much neck relief or the nut slots are too high, some fretted notes will be too sharp, and so when you use a capo all the relative harmonies between strings become distorted and you end up re-tuning again, only to chase the problem around to different strings and notes. The saddle is a whole different issue, and fixing saddle problems relating to tuning or intonation is rarely a minor adjustment. There are numerous considerations with the saddle to refine the “in-tune-ability” of the guitar.