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The notes of a diminished 7th chord form a 'circle of minor thirds'.

I've noticed that some composers modulate through one or more major triads built on successive minor thirds, e.g. major triads on F#, A, C, Eb, (and back to F#).

Is there much to be said about this harmonic sequence?

  • may be related to the Coltrane Cycle (I think that's Maj 3rds) or another Cycle from that era. The idea is also used by Pat Martino in his approach to chord theory (all chords are birthed from the dim7). Maybe read up on these ideas if you are interested. – ggcg Dec 27 '19 at 16:13
  • My piano teacher told me (at the age of 16) to practice the modulation by arpeggios C-> Cm -> C-dim7->Db->Dbm->Db-dim7 .... the chromatic scale up ... showing me that this is a way to modulate a half step up! Is this what you mean? – Albrecht Hügli Dec 27 '19 at 17:00
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Each chord change is to a chromatic mediant.

To this list of notable examples add: Gesualdo, Moro Lasso a Renaissance madrigal and Orlande de Lassus, Prophetiae Sibyllarum.

The sound isn't new or modern.

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  • Thanks, I'll have to check those. I can see those composers using one such modulation, but did they use a sequence of such? I noticed it in mid-20th century works by Howells, Vaughan-williams, Harris, etc. But they of course took a lot of influence from the 16th-century. – benwiggy Dec 27 '19 at 17:08
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    Not a literal sequence like a circle of minor third, but importantly not just a few oddball or unintentional occurrences. These pieces used the progression repeatedly, deliberately for chromatic effect. – Michael Curtis Dec 27 '19 at 17:46
  • @benwiggy, I should point out there are chromatic mediant progressions by both minor third and major third. Gesualdo has minor thirds, Lasso moves by major thirds (at least in the beginning, don't know about the rest.) – Michael Curtis Dec 27 '19 at 17:47
  • I thought a chromatic mediant was just III instead of iii, but you're saying it's essentially any chromatic alteration of any note(s) on the mediant triad. – benwiggy Jan 1 at 15:01
  • Chromatic mediants could be III, bIII, VI, or bVI from a major tonic. Just take a tonic, move the root up or down a major or minor third, use the same chord quality for both chords. Ex. from C to E, Eb, A or Ab all chords being major. – Michael Curtis Jan 2 at 21:44
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One outgrowth is that this sequence creates an octatonic collection. More specifically, it creates the half-whole octatonic collection beginning on the roots of the triads. In fact, you can get this octatonic collection by using major triads, minor triads, minor seventh chords, and dominant seventh chords all separated by minor thirds, a feature used by several Russian composers around the end of the nineteenth century.

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    One more way to get the diminished/half-whole scale is as a combination of two diminished seventh chords a semitone apart. – piiperi Reinstate Monica Dec 28 '19 at 15:06

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