What is the general standard in RNA for the natural minor key, as well as keys that are neither major nor nat. minor?
So in studying RNA, I found the major key pretty straightforward: I ii iii IV V vi viio.
But the minor key made things a little more confusing:
So if I understand correctly (from reading another thread), if:
situation = use RNA to describe chords built from the notes of the natural minor key, (e.g. C nat. minor key),
people might generally do one of the following:
method 1: ("Traditional notation" in above table)
use the same scale degrees from the (same root) major key (C major key), altering them to describe the natural minor key (C nat. minor key).
If C major key's last(?) diatonic chord, the leading tone diminished triad (B D F) = viio, then C nat. minor key's last diatonic chord, the subtonic major triad (B♭ D F) = ♭VII.
Chords with non-CDEFGAB roots need accidentals. e.g. "7" = last diatonic note of its major key / leading tone (B), while needing accidental to describe last diatonic note of nat. minor key / subtonic, so "♭7" (B♭).
method 2: (not in the above table)
assign new scale degrees to the nat. minor key, so diatonic triads: i iio III iv v VI VII.
C nat. minor key's last diatonic chord, the subtonic major triad (B♭ D F) = VII.
method 3: ("Alternative notation" in above table???)
know what the triads are, and chord quality is not listed. Unless otherwise specified, iii will always mean a diatonic 1 3 5 chord built off of the mediant (root). Upper/lower-case ignored?
C-major key: vii = leading tone diminished triad.
C-minor key: vii = subtonic major triad.
Methods 1 and 2 are more or less clear, but method 2 seems to me more intuitive when building diatonic chords in its own key. If RNA is dependent on a key, and the key does not change throughout a given sequence, then isn't method 2 the least ambiguous (shows chord quality) and most immediate/practical/relevant (it uses its own key)? I feel like method 1 sort of deifies(?) the major key, like an absolute point of reference.
The table above... I'm guessing the "Chord symbol" row is always upper-case/non-case-sensitive, and needs accidentals for notes non-diatonic to its (same root) major / taking the scale degrees from its major key. I'm not quite sure as for the "Alternative notation" section (shouldn't "I" be "i"? how to show non-diatonic chords' qualities?)
My main question is, apart from if hopefully I'm understanding things correctly,
What is the general standard in RNA for the natural minor key, as well as keys that are neither major nor nat. minor? (harmonic minor key(?), ascending melodic minor, non-western pentatonic(?)...)
I assume I can use method 2 for any scale, make it a key, forget about the accidentals, assign tonic = I/i, ... subtonic/leading tone/whatever last diatonic note = VII/vii (if heptatonic), and express chord qualities using upper/lower-case and symbols. This seems most intuitive (to me).
But resources I found use method 1 to describe chords built from the harmonic minor scale, but using the natural minor key as the point of reference, instead of the major key. Is this because there isn't a harmonic minor key? Or is there but just not used? Is the idea to use the closest key (i.e. most diatonic overlap), but that the key must be reasonably familiar to most (i.e. major/natural minor)?
e.g. if I wrote a chord progression in a song that uses only the diatonic notes of the A harmonic minor scale, how would I be expected to describe it using Roman Numeral Analysis?
A) method 1, A major key as reference (as in borrowing its scale degrees)
B) same method 1, but A natural minor key as reference
C) method 3, in A harmonic minor key. Can I do this? Does anyone? Would anyone care?
I would love to ask more, but this is perhaps already too long. Thank you immensely, I'm beyond thankful that this site exists!