Identify a chord as one of the augmented sixths, or null when it is none.
A chord qualifies when it sounds the lowered submediant of key in the bass,
its pitch classes are exactly one of the three sets built over that bass, and
its own letters spell the augmented sixth above it. All three are needed: the
same pitch classes over the same bass are an ordinary bVI7 when the tone ten
semitones above the bass is written as a minor seventh, and the letters are
the only place that distinction lives.
A chord naming no bassPc sounds its root lowest, which is how the two
conventions for that field — the sounding bass always, or only a bass that
differs from the root — are read alike here.
The root the chord is measured from is not consulted, so a chord voiced or
rebuilt around any of its own tones still identifies as long as it keeps its
spelling.
Identify a chord as one of the augmented sixths, or null when it is none.
A chord qualifies when it sounds the lowered submediant of
keyin the bass, its pitch classes are exactly one of the three sets built over that bass, and its own letters spell the augmented sixth above it. All three are needed: the same pitch classes over the same bass are an ordinary bVI7 when the tone ten semitones above the bass is written as a minor seventh, and the letters are the only place that distinction lives.A chord naming no
bassPcsounds its root lowest, which is how the two conventions for that field — the sounding bass always, or only a bass that differs from the root — are read alike here.The root the chord is measured from is not consulted, so a chord voiced or rebuilt around any of its own tones still identifies as long as it keeps its spelling.