Major Harmonic chords - Fourth degree, substitute for min/maj chord

Question

Please see below for F#/Gb Major Harmonic four note chords which I made. You will notice the fourth degree shows as a min/major 7th chord (which doesn't sound too bad). But, what is considered a good substitute for this min/maj chord? I ask as in minor harmonic chords, generally the 1st degree min/majo chord is usually substituted with a minor chord from what I have read, thanks.

Edit: Note: I've replace the previous layout which had incorrect spellings for Cb (B) and Ebb (D), thanks for the advice everyone!

Answer 1

This scale is more readable in F♯: F♯ G♯ A♯ B C♯ D E♯ F♯.

Anyway, this is an unconventional scale. I don't think you will find any conventional chord substitution for something that is unconventional in the basic form.

The seventh chord of the fourth scale degree is a minor major seventh chord (ivmΔ7.) Two thoughts about that particular chord on that fourth degree root:

• the chord's root and third are scale degrees ^4 and b^6, so while the tonic is major the basic subdominant sound is minor, iv I, which has that "borrowed chord" sound, but those two tones are also the minor seventh and minor ninth relative to the root on the dominant scale degree which put together can give us a dominant 7♭9 chord.
• When the subdominant chord is completed as a seventh chord it's ^4 ♭^6 ^1 ♮3 where the upper three tones ♭^6 ^1 ♮3 form an augmented triad.

You could just substitute the other subdominant chords the iiø7 (or iim7♭5.)

You can also substitute with dominant chords. If you play the plain dominant seventh chord in accompaniment, then ^4 ♭^6 in the melody will form a V7♭9, and melodically the other ivmΔ7 chord tones ^1 and ^3 would provide a V7sus4 or V13 type of sound respectively, so you can get a bunch of dominant flavors. Also in the dominant camp you could play the viio7 which contains tones ^4 ♭^6.

But, another interesting possibility is exploiting the upper part of ivmΔ7, the augmented triad part ♭^6 ^1 ♮3. Because of the symmetry of augmented chords and scales there is a sort of vagueness to roots in the augmented context. You can sort of treat the associated whole tone scale as all "fitting." In other words take chords from the whole tones scale built from the ♭^6 degree. One of those chords would be ♭VI7♭5.

Obviously there could be some potential clashing of the natural ^4 or ^5 of the original harmonic major scale and the ♯^4 of the substituted whole tone scale, but the interesting thing is ♭VI7♭5 is like the French augmented sixth chord (or tritone substitution from jazz) which could lead to a dominant chord. That means ♭VI7♭5 could function like a pre-dominant which is the same function as the minor subdominant iv which is the basic fourth degree triad in harmonic major. So ♭VI7♭5 can sub for ivmΔ7 while maintaining the same basic function and general whole tone scale sound. In F♯ it would be normal ivmΔ7 as BmΔ7 and sub D7♭5, something like BmΔ7 BmΔ7 F♯Δ7 | D7♭5 C♯7♭9 F♯Δ7.

Answer 2

I guess you're making 4-note chords from each degree of the diatonic major scale in key G♭.

The first thing to do is make sure all the diatonic names are correct. Looking at G major, it's G A B C D E F♯ G. So every one of those needs to be flattened - importantly, in name.

So, we get G♭ A♭ B♭ C♭ D♭ E♭ F ♮, G♭. Please note - not a B or a D anywhere!

And - IV will always be maj7, using the standard major. However, since it's harmonic major, those notes in that key are C♭ E♭♭, G♭ B♭, giving mM7, as you say - just spelled incorrectly, but sounding the same!

Armed with these names, there are some errors in what you've written. Care to have another go with that?!Golden rule - each note has its own dedicated letter name (hence no D and D♭.)

Correction - it's the harmonic major! So lowering the 6th degree gives not E♭, but E♭♭.

That will alter the chords which would contain that 6th note - those based on the 2nd, 4th and 6th degrees (A♭, C♭ and E♭♭) and 7th degree, which as a 7th chord, would contain E♭♭.