A chord carrying its own tone spellings is read by them, since the degree it
writes a tone as is the degree that tone plays: the ten semitones above the
root of a German sixth are written five letters up, so they are its sixth and
not a seventh owing a step downward. Everywhere else the role is derived from
the pitch's interval above the chord root, reduced modulo 12. A major sixth
(9) reads as a sixth for sixth chords but as a seventh for a
diminished-seventh chord; ninths and other tensions have no basic role and
return null.
Determine a pitch's harmonic role within a chord.
A chord carrying its own tone spellings is read by them, since the degree it writes a tone as is the degree that tone plays: the ten semitones above the root of a German sixth are written five letters up, so they are its sixth and not a seventh owing a step downward. Everywhere else the role is derived from the pitch's interval above the chord root, reduced modulo 12. A major sixth (9) reads as a
sixthfor sixth chords but as aseventhfor a diminished-seventh chord; ninths and other tensions have no basic role and return null.