This is one thing that has always bothered me, why are VI and bVI 2 different chords in major but the same chord in minor? That makes no sense to me. I mean it does but it also doesn't. If you view major as the one and only true scale used and that the rest are just rotations of that scale or to put it in musical terms, modes, then yeah, Ab major in C minor would be labeled as bVI. I however rarely ever come across situations where minor is being used modally outside of Renaissance.
Even in the Baroque, the only "modal minor" I see used is Dorian, which I realized when I saw 2 separate scores by Bach with the name Toccata and Fugue in D minor, where one was in D Aeolian(the very well known one) and the other was in D Dorian(which, I notice a resemblance between the Dorian Toccata and the subject of the Aeolian Fugue, whereas the Dorian Fugue more closely resembles Fugue in C minor WTC Book I). Phrygian, another close modal relative of Aeolian, I just don't see outside of Modern where it's often altered to Phrygian Dominant, and Renaissance.
As soon as I get to Classical and Romantic Eras, minor and major become distinct in everything, not just the harmony, but the way the harmony is treated. As an example, take vii°7. In Major, I typically see this used in 1 of 2 ways, those being modulation to minor and as an extension of the dominant zone(V7 -> vii°7 -> I for example). Whereas in Minor, I often see vii°7 being used as the one and only dominant chord in a phrase, especially in Beethoven.
This is why I a) always mark major or minor in my harmonic analyses and b) don't think that bVI in minor should be the same as bVI in major. I mean this is my instinct for bVI, VI, and #VI in major and minor:
- bVI in Major -> Borrowed from parallel minor, so in C major, it would be Ab major
- VI in Major -> Major chord on the diatonic submediant note, so in C major, it would be A major
- #VI in Major -> Unusual way of spelling bVII, but it would make sense if for example it's a chromatic mediant to analyse it as #VI
- bVI in Minor -> Equivalent to the diatonic V chord, but again, only in situations like chromatic mediants, where I would want to emphasize the third relation and not imply that it is a dominant chord would I do this(example, G major shows up in a C minor passage after Eb major and it comes back to that same Eb major without going to C minor first, but ultimately doesn't modulate away from C minor through the passage, the G major is treated as a Chromatic mediant of Eb and not as the dominant of Cm, so I would be happy labeling it as bVI to get the function across)
- VI in Minor -> Diatonic submediant chord, no need for the flat in the roman numeral
- #VI in Minor -> Major chord on the sharpened submediant, so in C minor, it would be A major
Now in practice, I find it rare that Chromatic mediants are used outside of modulation in Classical and Romantic era pieces, especially when it isn't a chromatic mediant of the tonic, and so the only ones on this list that I would see with relative frequency are bVI and VI in major and VI and #VI in minor.
But to get back to what I was asking about, why is it that bVI and VI in minor seem to be interchangeable when the bVI only really makes sense in the "Minor as a mode of Major" type of analysis as it would mean something totally different in the "Minor as a distinct scale" type of analysis(which is what I myself use as for reasons stated above, Minor tends to be treated totally different from Major in terms of the harmonic motions), namely a chromatic mediant chord that sounds the same as the dominant triad but is not used like a dominant chord and is not in a modulating passage? I mean, even amongst analyses that treat minor and major as distinct scales, I still see bVI being used equivalently to VI which makes no sense in that kind of analysis. But only in minor, in major they are distinct in all analyses.
