Previously we used a heuristic for choosing pitch names based on the
major scale degree, minimizing radicals. So, for example, in the key of
Gb, we render the 4 as Cb rather than B because Bb is the 3 of Gb. In
other words, we want 1:Gb, 2:Ab, 3:Bb, 4:Cb instead of re-using B. This
is standard practice in western music notation.
When rendering non-diatonic notes we prefered choosing the version that
minimized the radicals. Again in the key of Gb we would choose to render
E as E (the #6) rather than considering it as Fb (the b7) and choose to
render D as D (the #5) rather than E𝄫 (the b6). This was chosen to
reduce the number of unusual radicals like 𝄫.
However, in practice this leads to unusual charts because it is more
common when writing chordal harmony to use the b6 rather than the #5.
Similarly the b7 is far more common than the #6. This is, I think, due
to the prevalence of the major scale and minor scales and the fact that
the minor scale is built from flatting the 3, 6, and 7 of the major
scale. So when thinking in a key-center agnostic manner (like numbers)
we almost always think about these altered scale degrees as being
flatted relative to the major scale, not sharped. Because of this, in
the key of Gb, we would prefer to render a b6, b7, 1 chord walkup as
E𝄫, Fb, Gb rather than D, E, Gb.
This change redefines the heuristic used to name chord pitches to follow
a heuristic that covers all pitches in the octave based on scale degree:
1, b2, 2, b3, 3, 4, b5, 5, b6, 6, b7, 7
- Non-diatonic pitches are supported using Nashville numbers (#5).
- When using Nashville numbers chord variants with non-diatonic roots
are now recognized (e.g. b7)
- Pitch rendering is now aware of key centers. For example, F# is F#
rendered as F# when in the key of G but Gb when in the key of Ab.
