How to Tune a 12-String Guitar. The rich sound of a twelve-string guitar is produced by simply holding two strings at one time, a task that is not as difficult as it sounds. The most challenging part is keeping all twelve strings in tune.
Use a guitar tuner to tune your twelve-string guitar. No matter how well you can tune your six string with your perfect ear, you will find yourself extremely frustrated and spending far too much time trying to tune your twelve string without an electric tuner.
Tune your strings one octave apart, except for your high "B's" and high "E's," which are both tuned as normal. For example, tune the top low "E" string as you would a regular six string guitar, and tune the second lower "E" string one octave higher. Repeat the double octave tune with the "A's," "D's" and "G's." Tune both "B" strings and both high "E" strings to the same octave as you would a regular six string guitar.
Begin tuning at the "G" strings, working down the "B's" and "E's" and then going back to the "D's," "A's," and low "E's." With twelve strings, the pressure on the fingerboard is much different than on a six string guitar. If you tune from low "E" to high "E," you will find that your upper strings are out of tune again by the time you are finished. Tuning center down, center up will help prevent stretching and pressure that will quickly cause your strings to go out of tune again.
Maintain your tuned guitar for as long as possible by tuning up, not down. For example, when you begin working on a string, loosen the key a bit first so that you are beginning tuned down. Gradually tighten the key until you reach tune. If you overshoot and go past the target, loosen the key again tuning up. Tuning up will ensure that your guitar holds the tune longer, as strings tuned down tend to loosen quickly.
Keep an extra high "G" string or two on hand, as these are the smallest gauge strings made for guitars and will break often.