i was writing chords when I came up with this progression:


i understand why the V/vi-IV works--because there is only a one note difference between vi (which V/vi usually resolves to) and IV.

however, I found that replacing the V/vi with V/iii also works quite well, making the whole progression:


this makes no sense to me as first of all, the chords V/iii and IV are a tritone apart from eachother, yet still work well in conjunction in this progression.

also, V/iii has very little in common with the 2 main chords that resolve to IV nicely that come to mind, V/IV and V/vi. the only similarity they have is V/iii and V/vi both have the 7th major scale degree.

voice leading withholds some explanation, but the only notes that resolve by a semitone are the root note of V/iii resolving up to the 5 of IV and the 5 of V/iii resolving down to the root of IV (see notation in C below). enter image description here

this is the only plausible explanation i can find, does anyone have any other things that could explain this?

  • V/iii to iv is also iv0/iv to iv, a plagal-type movement. Every movement by fifths (up or down, or tritone) sounds a bit like a diatonic V-I or IV-I in some key (with minor or diminished chords.) This isn't a "why" but an analogy or sorts.
    – ttw
    Commented Jun 8 at 1:14
  • interesting! by iv0 do you mean iv diminished?
    – alistato
    Commented Jun 8 at 1:50
  • I think V/iii is IV/IV. If it were diminished it would just be called vii° Commented Jun 8 at 1:55
  • @ToddWilcox sorry, i'm confused. isn't IV/IV the same as bVII?
    – alistato
    Commented Jun 8 at 1:59
  • 1
    Related due to having the same root movement and use of triads: music.stackexchange.com/questions/64464/…
    – Dekkadeci
    Commented Jun 8 at 7:29

2 Answers 2

  1. The first observation to make is that the chord being called V/iii is a half-step down from I: e.g., if I is C major, then "V/iii" is B major.

  2. A second observation, but a subjective one, is to hear the progression "V/iii -> IV" as actually being "bII/bVII -> V/bVII". For example, relative to the key of C major, try playing B major -> F major -> Bb major (or, more precisely, CbM -> FM/A -> BbM). To my ear, this resolves nicely, and notice the chromatically descending bass.

  3. However, instead of resolving to bVII, the V/bVII serves as a pivot chord to get us back to the starting key (V/bVII = IV).

I:     IV  V  I              IV     V  I
bVII:            bII/bVII  V/bVII
  1. If we really want to push the interpretive envelope, then we could call I V/V/bVII and also view it as a pivot chord. Thus we have three chords interpreted in the key of bVII: two predominant chords (V/V and bII) and the dominant (V/bVII) but which never resolve within that key.
I:     IV  V    I                  IV    V  I
bVII:        V/V/bVII  bII/bVII  V/bVII
  • Jazz people would call this a tritone substitution, right? (bII7 is a tritone sub for V7) Commented Jun 8 at 2:50
  • 1
    @ToddWilcox Yes, but I hesitated to call it that since the seventh is missing. The heart of tritone subs is that the 3rd and 7th swap rolls. However, I think one could make a perfectly valid case for the "V/iii" chord actually being a tritone sub for the IV chord. In a jazz or pop setting, where the rules are looser, that would be entirely reasonable on its own — no further explanation needed.
    – Aaron
    Commented Jun 8 at 2:57

Stepwise motion, aka parsimonious voice leading. In this example, would be better blended if B->A, D#->C and F#->F - try it! :D

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