Harmonic Major Applications

I just watched a Tom Quayle video on this topic that contains some good information but needed some translation before it made sense to me. I thought I'd provide the translation for anyone else who found it useful.

Here's the video:

Tom's fundamental point here is that in a given key there are three different diminished chords and each has a different function, and there's a Harmonic Major application for each one.

The first function he calls "tonic" diminished chords: in C that would be C dim, Eb dim, Gb dim and A dim. For this situation he recommends G Harmonic Major.

The second function he calls "flat nine" diminished chords: in C that would be Db dim, E dim, G dim and Bb dim. Here Tom wants us to play F Harmonic Major.

The third function he calls "nine" diminished chords: in C that would be D dim, F dim, G# dim and B dim. To most of us this looks like a tritone sub: D dim standing in for Db7, which is standing in for G7. The scale here is C Harmonic Major.

All this is tremendously confusing for those of us who like thinking in terms of scales rather than relative modes. So let's unpick it:

• On "tonic" diminished chords, play Lydian Minor
• On "flat nine" diminished chords, play Kosalam #5
• On "nine" diminished chords, play Dorian b5

That may or may not seem simpler to you, but it seems simpler to me.

A question remains about whether this analysis makes any sense. The function of a diminished chord is usually defined by how it resolves, not by its relation to the key (which, if there's a diminished chord about, is probably about to change). The scales don't really match the diminished chord's tones very closely, so there's probably a simpler interpretation of what's going on and why these sounds "work". But that's for another day.

[Update: It's been pointed out to me by email (thanks, Adam!) that Lydian Minor is more commonly called Lydian Diminished. This is an inheritance from George Russell's Lydian Chromatic Concept of Tonal Organization. I don't have Russell's book handy (it's not really my jam) but I suspect Quayle's approach here may be derived from it, or at least related to it in some way. So that name is probably more appropriate here. But it's called "Lydian Minor" in the book, so I'll leave it there to make it easier to find with Ctrl-F.

Incidentally, what some others call "Lydian Minor" is the natural minor with a #4, i.e. 1 2 b3 #4 5 b6 b7; in the book this is called "Shanmukhapriya". This is a matter of convention; I think of "Lydian" being the name of the scale and "minor" being an alteration (lowering a major third to a minor third). Using this method, "minor" is taken to be the scale (natural minor) and "Lydian" means "raise the fourth". In the end, there's just no standard approach to naming scales beyond the handful that have been in regular use for a century or more, so it's always safest to acknowledge the different variants when you can. ]