Method and apparatus for fully adjusting and providing tempered intonation for stringed, fretted musical instruments, and making adjustments to the rule of 18

A method of intonating and tuning a stringed musical instrument having a body, strings, and frets, the method comprising tempering the strings according to a Feiten Temper Tuning Table with a specific pitch offset formula where for at least some of the strings pitch deviations other than an octave relationship exist between a pitch at the open position and a pitch at the 12th fret.