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Here are some rules I have encountered regarding typical common common-practice root movement (in order of declining strength):

  • Upward perfect 4th, downward perfect 5th
  • Downward perfect 4th, upward perfect 5th.
  • Upward second.
  • Downward third.
  • Downward second.
  • Upward third.

I am assuming these only apply to the seven major-scale triads. Are such rules applicable when we change our harmonic palette? I am specifically interested in how they translate to the chromatic-minor system, which (if I understand correctly) consists of major triads built on every step of the natural-minor scale.

  • Can't say I've heard of this "chromatic minor" under that name, but I have thought of exactly what you're saying (I-II-♭III-IV-V-♭VI-♭VII). I have no idea how the interval relationships would work, beyond what normally happens since almost all of the chords are borrowed. – user45266 Apr 14 at 0:12
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    OP, your phrasing of your understanding of what the "chromatic-minor system" is matches pretty closely to the phrasing I found in this web page I found from a Google search: books.google.ca/… – Dekkadeci Apr 14 at 6:53
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    @Dekkadeci Great find! Certainly interesting how the author takes on the challenge of non-diatonic chords in popular music. – user45266 Apr 14 at 22:48
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When I first read the term "chromatic minor" in the question title I was dismissive of the idea. Then I read the textbook description in Stephenson's What to Listen for in Rock and I realized it's a good description of rock harmony.

I don't think this tonality is as strange as the other answers and comments suggest.

First. let's recognize chromatic minor is a description of classic rock, a musical style most people are familiar with. If you are familiar with the sound of The Rolling Stones, The Who, etc., this tonality should not sound bizarre. So, let's reserve judgement and compare with common practice harmony and see what we get.

There are 9 chords in chromatic minor. The chords of the tonic and supertonic each have two variable forms so we get 4 chords from those scale degrees, then single chords for the other scale degrees give us the remaining 5 chords.

For the purposes of this comparison I will consider the V chord - the major triad with a raised leading tone - a diatonic chord in minor key music. Technically it is chromatic, but in common practice minor key music the V is an essential, primary chord, so I will consider it diatonic.

The five chromatic minor chords i, bIII, V, bVI, and bVII are diatonic minor key chords. The major triad I can match up to a Picardy third final tonic chord in common practice, but that is not how the chord is used in chromatic minor, so this is a point of difference between the two systems. The two supertonic chords N and major II certainly are not diatonic, but they are common chromatic chords in minor key harmony. However, it needs to be pointed out that Stephenson uses the II symbol specifically instead of the secondary dominant V/V symbol to indicate the chord's identity in chromatic minor is not a secondary dominant. This is another difference between the two systems. Finally the major IV can be found in minor key harmony, but in common practice the chord can frequently be a minor triad. The subdominant in chromatic minor is fixed but in common practice minor it is variable.

Of the 9 chromatic minor chords, only three - I, II, and IV - stand out as not aligning with common practice minor key harmony. In other words, if we eliminate only the I, II, and IV chords from chromatic minor, we could make common practice harmony with the remaining 6 chords i, N, bIII, V, bVI, bVII. The main limitation is not having minor subdominant chord variants like iio or iv.

It was pointed out in another answer that chromatic minor uses all 12 chromatic tones. But this is in no way unique or strange compared to common practice minor. In common practice minor, scale degrees are altered all the time in normal harmony ^2 lowered for N6, ^3 raised for V/iv, ^4 raised for V/V and _augmented 6th chords, ^6 raised for IV6, and ^7 raised for major V. Those alterations and the associated chords are normal in common practice minor, and they can be used without necessarily modulating to another key. When those alterations are all combined the complete chromatic scale is utilized. So, using all the chromatic tones is not a unique property of chromatic minor.

Also, regarding chromatic scale degrees, all scale degrees in chromatic minor exhibit alterations except the tonic ^1 and dominant ^5. Those are the two most important tonal degrees. This is another point of similarity between chromatic minor and common practice.

Now let's get to the question of root progressions.

I will limit my comparison to what I think are the commonest root progressions: descending (↓) 5th, ↓4th, ↓3rd, and ascending (↑) 2nd.

↓5th and ↓4th: except for the tritone interval between bII and V and II and bVI all these progression are diatonic.

↓3rd: progressions i to bVI and bIII to i are diatonic, but all others are non-diatonic chromatic mediant progressions. Chromatic mediant chord pairs always share the same chord qualities so this is an important characteristic of chromatic minor. In common practice, ↓3rd progression result in a change of chord quality. This is probably the biggest difference in comparing the two systems.

↑2nd: this seems a bit trickier to compare, because in common practice root progression by seconds is more circumscribed that other movements. Chord need to be in first inversion or need to involve specific roots like i to iio6 or iv to V to fit the common practice norms. Anyway, all the ↑2nd progressions in chromatic minor which move by whole step can be interpreted as IV to V, because there will be a hypothetical I a perfect 5th below the V, the exception is i to II. The half step ascents in chromatic minor are not diatonic except V to bVI.

It's hard to quantify how much overlap exists between chromatic minor and common practice minor, but I think I have presented a substantial amount of overlap. If the tonic chord is minor i you could have a lot of chromatic minor progressions that match pretty closely to common practice. In fact I think the bigger difference is voice leading. Rock uses mostly root position chords while common practice has a strict system of counterpoint norms.

Stephenson describes chromatic minor as "consisten use of a particular triad [chord] type... at the expense of scale purity." There is another super common tonality which does the same: the blues. The blues uses all dominant seventh chord on roots ^1, ^4 and ^5, and while the triad portions of those chords are diatonic the sevenths are not. All the chord qualities are the same but the sevenths break the "scale purity." If we recognize the blues works with a "chord type versus scale purity" concept, then by comparison chromatic minor may seem less strange. This has no bearing on a comparison to common practice, but it's interesting food for thought.

I think the biggest difference between chromatic minor and common practice minor is the ↓3rd chromatic mediant progressions. Those really run contrary to common practice harmony. The other critical differences are the fixed quality of the subdominant and the use of a major I tonic. Otherwise, many chromatic minor progressions can be similar to common practice progressions.

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Note: I'm going to treat the "chromatic-minor system" as a very specific and strictly defined tonality. It has considerable overlap with common rock harmonic devices, and User Michael Curtis' answer is quite comprehensive in that regard.

[...] the chromatic-minor system, which (if I understand correctly) consists of major triads built on every step of the natural-minor scale.

I hope you have your terminology correct, because I'm going to analyze this "chromatic minor" assuming that your description is correct. If you meant some other weird theory term, oh well.

So, in C chromatic minor (never heard of that name, btw) we have:

  • C-E-G
  • D-F♯-A
  • E♭-G-B♭
  • F-A-C
  • G-B-D
  • A♭-C-E♭
  • B♭-D-F

I've not heard any music written specifically with this tonality, so I'll draw some observations from what I know.

For starters, we have the I chord. Cool. We also have the IV and V. Cool cool, so far so good. Then the feces hit the fan.

The II chord. This can be used as V/V, I guess, so I imagine it would have a subdominant function. That F♯ seems like a clear leading tone to G.

The ♭III chord. This can sound kind of bluesy, although it's a product of modal mixture, so it can sound pretty interesting on its own. I can't see that cleanly resolving to the tonic or the dominant, but it could be part of a ♭III-IV-V-I walkup (or I-II-♭III-IV).

I hope you know how the IV and V work, and this is probably as close as this weird scale is going to get to common practice harmonic ideas.

♭VI contains A♭, which is a half-step above G. For that reason, I think it would also have a subdominant function. Also, it's a tritone substitute (kinda, but with no seventh) for II, and it's also kinda the augmented 6th chord, or at least one could certainly use it as one. Also, ♭VI-♭VII-I is cool too (hehe).

♭VII could have a dominant function, I imagine, with its F resolving to E. That's kind of weak, though, especially compared to V-I. It does have that whole step up momentum, though, and its parallel structure means you can play with some pretty cool melodic ideas (like transposing the melody up a whole step and making it sound really bright).

This is pretty far from the common practice guidelines' jurisdiction. In general, no, those guidelines don't really hold, especially because those "up/down by a third" statements get ruined by the many, many chords whose roots have been altered.


Quick Facts:

  • This tonality uses every note of the chromatic scale no matter what root one starts on - except the lowered supertonic.
  • Every chord, obviously, is major.
  • ♭III-IV-V is a transposition of ♭VI-♭VII-I, making modulation a breeze.
  • 4 of its 7 chords are borrowed/modal mixture.

Also, its modes, which are a nightmare to consider, are:

  • I-♭II-♭III-IV-♭V-♭VI-♭VII
  • I-II-III-IV-V-VI-VII (for which I propose the term "chromatic major")
  • I-II-♭III-IV-V-VI-♭VII
  • I-♭II-♭III-IV-V-♭VI-♭VII
  • I-II-III-♯IV-V-VI-VII (this has to be one of the brightest tonalities out there)
  • I-II-III-IV-V-VI-♭VII

You could even name them by their modes, e.g. chromatic Ionian, chromatic Dorian, chromatic Phrygian, chromatic Lydian, chromatic Mixolydian, chromatic Aeolian, and chromatic Locrian...

Eww.


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    If there is such a thing as a 'chromatic minr' iyt may be what you describe. You've used just about every note available in your triads! Trouble is, there would appear to be no natural (excuse the pun...) home-sounding root, therefore little tonality. But a brave answer nevertheless! – Tim Apr 14 at 7:26
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"Chromatic-minor" is a term I've not heard before (and I can't make any meaning of it), but, yes, overall the same progression rules apply whether it's major or minor tonalities and in a minor tonality we build progressions with chords built (mostly) on the natural minor scale.

But there are specificities, namely the the very important exception of the V degree, where in general (almost always, in common-practice) we use a V (major triad) chord built with a raised 3rd degree (i.e. the 7th degree of the scale), rather then the v (minor 5th degree triad) that we would get with the pure natural minor.

This is because in functional harmony we need the so called leading-tone, i.e. the 7th degree of the scale, to "resolve" upwards by exactly one semitone to the tonic. That happens naturally in a major mode. But in a minor mode, the natural 7th is one tone, not one semitone, below the tonic.

So, melodically, almost always when the melody moves upward from the 7th to the tonic, we need to raise the flatted 7th degree. If the melody comes from the 6th degree, to avoid the augmented-second interval the results by raising the 7th, we also raise the 6th, resulting in the upward part of the so called melodic minor scale (the downward part is just the natural minor, as, when going downward, we don't need the leading-tone function).

Harmonically, we also need to raise the 7th degree to get resolving perfect cadences (V-i progression). Using a v-i progression would take us to modal harmony (aeolian or natural minor mode, in this case) and that's an aproach totally alien to common-practice funtional harmony.

This does not mean that every chord on the 5th degree must be major, as it's possible to have such a chord and not resolve to the tonic in a perfect cadence. But in common-practice it is rare to find a V chord that it's not major.

Now, going back to the initial question, the way triads are built in a major and minor tonalities is:

  • degree 1 2 3 4 5 6 7

  • Major mode I ii iii IV V vi viio <--- "o" means diminished triad

  • Minor mode i iio III iv V VI VII <--- the V as per the above explanation

You can build the same progressions with these chords in a minor tonality as with the equivalent ones in the major tonality.

  • Note: regarding the "strenght" rules, I wouldn't state them exactly like that, but that's not the the issue of the question, so I'll not go into that in this answer. – José David Apr 14 at 1:55

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