Se ho capito bene quella che Metheny ha usato sull'acustica e' un "adattamento". La tuning originaria nasce sulle pedal steel ed e' cosi': "The standard Nashville E9 tuning for ten string pedal steel guitar is B-D-E-F♯-G♯-B-E-G♯-D♯-F♯.
"Nashville Tuning" can also refer to the practice of tuning the wound EADG strings on a standardly tuned six-string guitar an octave higher. This is usually achieved by replacing the standard-gauge string with the equivalent octave string from a 12-string set".