What is the functional role of the subtonic chord?

Question

In this chart

the subtonic major chord can come before the mediant and submedian chords. Does this imply that it has a tonic functionality? If so that seems counter-intuitive; it seems to share more in common with the dominant chord than the tonic. On the other hand, if it's a dominant function, why would you have a i-VII-III... progression? Wouldn't it make more sense for the VII to fall later, towards the end of the phrase.

(Also I'm assuming that the VII actually refers to the bVII chord, but if I'm wrong please correct me on that)

Answer 1

I basically agree with Michael Curtis's answer. But I might summarize/classify the uses a bit differently:

1. The most common use of VII in minor is actually not as functional VII at all, but rather as the dominant of the relative major. So the i-VII-III progression mentioned in the question is often best viewed as temporary tonicization of the relative major. For example, if you were in A minor, but then had a G major-C major progression, that effectively feels like you're making a (perhaps very temporary) hint of a V-I toward C major. As you may know, minor key pieces very commonly have a secondary key diversion to the relative major, and "VII" is basically the easiest route there. This harmonic progression (i-VII-III, otherwise interpreted as i-V/III-III) is all over modal music and early tonal music, and it can happen in modal pop styles today that oscillate between major and minor. Bottom line: in that case, it may be labeled as "VII," but it's often functionally acting like V/III.
2. The next most common use is probably sequences. The charts in the question are hinting at that, i.e., a i-iv-VII-III-VI-ii^o-V-i circle-of-fifths sequence. Chords in sequences aren't really "functional" either -- they are driven more by the repeated harmonic pattern rather than by predominant-dominant-tonic motion.
3. The third use is as an alternative harmony in descending tetrachord progressions, i.e., progressions where the bass descends from scale degree 1 down to 5 (over four notes, the "tetrachord"). These sorts of bass lines show up everywhere, and one minor key pop harmony version that sometimes gets used runs down i-VII-VI-V. Once again, this motion isn't particularly "functional," as VII is a passing chord just used to harmonize a scale step in the bass in parallel chords.
4. So far, none of these uses of VII tend to actually give VII a unique function. The only true functional uses of VII are perhaps found in some variant cadential progressions. There are examples of modal cadences that use a VII-i progression to substitute as a sort of V-i cadence, and jazz sometimes uses the "backdoor" cadence VII⁷-I (in major or minor). In these cases, VII is arguably a dominant substitute, containing two notes of the V⁷ chord.
5. In a slightly different fashion, VII can sometimes appear functionally as subdominant of subdominant. I've mostly heard this clearly in things like gospel cadences that emphasize IV-I instead of V-I. In that case, it's not unheard of to create a VII-IV-I progression (or variants), generally in a major key (rather than minor). I don't know that there's a specific name for this function, other than the fact that it's sort of "IV of IV," so there's a kind of mirroring going the other way around the circle of fifths (i.e., VII-IV-I rather than ii-V-I, where the ii chord is based on the dominant of the dominant).

In sum, VII can act a bit like a dominant or predominant at times, but mostly it doesn't have a strong distinct function in a minor key. The vast majority of its appearances (at least in classical harmony) are in sequences or sequence-like progressions, or as a pathway (as secondary dominant) to the relative major.

Answer 2

Generally the "functional role" refers to "functional harmony" where chords have a "function" in a chord sequence. (I don't much think the word "function" is the best, but it's what people call the phenomenon.) The main idea of functional harmony is that phrases are marked with some type of cadence, mostly cadences with some type of V-I or V-i finish (as your charts show.) This cadence may be modified using a V7-I or V7-i or a IV-V-I or ii65-V7-I or ii06-V-i in a minor key. For historical reasons, the functions are called tonic, dominant, and predominant (or subdominant which describes the scale position instead of the compositional position of the chords.) The shortest piece would (in this formulation) tonic-predominant-dominant-tonic structure (this is very simplified). Phrases using I-IV-V-I are not uncommon. Then the idea is to expand parts, I-IV-V-I-IV-V-I which is just a repeat of the first progression or I-vi-ii-V-I-ii-V-I which expands the predominant chords into vi-ii in the first phrase.

Chords are functionally classified by their use(important), not their name (unimportant but convenient). (An incomplete list): The tonic chord in a major key is I (sometimes vi can act a bit like a tonic as will be illustrated below; it can have predominant function as above I-vi-ii-V or I-vi-IV-V). The dominant chords are V,V7,vii0,vii07,vii0 in general. The predominant chords are IV,ii,vi, (sometimes), I64 before some form of a V-I. (The minor mediant is rare in this style except in sequences.) In a minor key, i is the tonic; V,V7,V9,vii0,vii06 are some of the dominants, iv,VII,VI,ii0,ii06,ii,ii6,i64, are a few of the pre-dominants.

Chords may be used in more than one context. In the pop (though going back before Vivaldi) progression I-vi-ii-V, the vi acts like a predominant by extending the ii-like feel. In a phrase like I-ii-V7-I-ii-V7-vi-ii-V7-I, vi acts like a tonic in the V7-vi pattern (a deceptive cadence) but overall may be seen as a predominant in the vi-ii-V7. Both views are correct simultaneously.

The "function" name may be applied over a region rather than just a chord. Music patterns are to some extent recursive and operate over different scales (mathematical scales, characteristic length, not an ordered set of notes). A common pattern is I-V-I-vi-ii-V7-I. The I-V at the beginning doesn't act as a cadence; it really just extends the I. Some authors (and I agree though I'm not an author) like to call these "passing" chords. This gives a fourth function "passing." One can see this in pieces using a repeated cycle of fifths (or fourths depending on which direction one prefers) in a minor key. One often gets i-iv-VII-III-VI-ii0-v-i-iv-VII-III-IV-vii0-V-i. The second V-i is marks the end of a section and uses a cadence. The root movement of v-i in the middle doesn't sound like it ends the piece because the dominant (chord on the fifth note) chord is minor.

The common ii-V-I pattern in classical and jazz music (other genres) is a short example of functionality. This (and other patterns I presume) can be used to give a short coloristic sound to a piece. Sometimes one sees a pattern like II7-V7-I in a piece; this looks like a ii-V7-I but the II7 is the dominant of the V (V of V is the terminology and V/V the symbol). It keeps the cadential ii-V-I feel but digresses (with a sharpened fourth scale step) a bit just to provide interest. It's not a true key change (unfortunately called modulation for historic reasons) because it doesn't last long enough.

Answer 3

Let's set the key to C minor.

When the given key uses a minor key signature you don't need to prefix a flat on the Roman numeral, it's assumed from the key signature. So, in C major C: bVII the flat shows the chromatic lowering of the root from the major key signature, but in Cm: VII the minor key signature already sets the flat on Bb so you don't put the flat prefix on the Roman numeral.

Also, let's be sure to not confuse VII a Bb triad with v6 (the minor dominant with Bb in the bass.) v6 is common with a descending bass, like Cm: i v6 iv6 V.

If you are working with common practice harmony, VII has a tendency to sound like the dominant of the relative major. In other words, the Bb major chord to Eb major, rather that sounding like Cm: VII III sounds more like Eb: V I.

On those flow charts, notice how iii and VII are both at the far left away from the primary tonal chords I, V, and IV. They are both out in the modal nether-regions and not very strong for defining the tonality. They are modal or secondary chords of a key. Functionally they are both pre-dominant. From them you would move along the flow charts to the left to get to the dominant function, and then the tonic function.

The VII can also act like a alternate dominant with a modal flavor.

A common form that uses VII is passamezzo antico where it appears both as a modal dominant and as the dominant of III.

A similar kind of harmony happens in Handel's sarabande in the suite HWV 437, but it also involves a harmonic sequence.

Dm: [ i V ] [ III VII ]

Harmonic sequence is another common way modal chords like VII and iii occur. In terms of function that can make them sort of ambiguous, because harmonic sequences are often used to change key.

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...why would you have a i-VII-III... progression?

Don't treat those flow charts as a practical guide to harmony. Think of them more like very abstract representations of two basic music theory ideas: the fundamental tonal harmony progression is root movement by descending fifth, and functional harmony flows pre-dominant to dominant to tonic.

If you take the charts literally, then you can't even get something as fundamental as the Handel example Dm: [ i V ] [ III VII ].

Keep in mind the flow charts makes no reference to phrases or barlines. i is often the end rather than the start. Something with a barline hinting at phrases, like Cm: ...V7 i | VII III... gives a bit of context where i VII III could make sense.