Theory question on Equinox

[DONZI97]

So I've been playing for about 3 years, taking lessons for about 2, and play in a rock cover band. I have been wanting to get into Jazz, and starting to get into it with my instructor who has started me off with ii V I progressions, then moved to ii V I vi's. Between him and reading here, I know the basics about theory. My question is about Coltranes Equinox, and how does the flattened vi come into play? I don't understand it. Its a cool tune, and believe it or not I found it through a Clutch cover.


Equinox - YouTube

[bassbrad]

The flatted vi chord is a not too common blues change, Coltrane uses it in 'Equinox', Miles used it in 'All Blues' and at least one other tune. BB King used it in 'The Thrill is Gone' and I am sure there are many others.
For the bass player we would move up that half step letting the melody or soloist ride thru to add harmonic tension.

[DONZI97]

Sweet, thanks.

[jacojbass]

It is an inherent chord change in minor blues (bV7 V7 i) and is very common to MINOR blues. one could also hear this as a sub V of V...hope this helps.

[Audiophage]

Originally Posted by jacojbass

It is an inherent chord change in minor blues (bV7 V7 i) and is very common to MINOR blues. one could also hear this as a sub V of V...hope this helps.

Yeah, it's a little nicer sounding for the minor cadence than the half diminished ii chord that exists in minor.

[sammyp]

Originally Posted by jacojbass

It is an inherent chord change in minor blues (bV7 V7 i) and is very common to MINOR blues. one could also hear this as a sub V of V...hope this helps.

right! it's a more tasty lead to the V chord!

[shwashwa]

you could think of it as a sub for the ii chord. in C minor you would have D-7b5 to G7b9 to Cmin7. the flat 5 of D is Ab which is a very strong note in the D-7b5. its become very common in jazz to play the major 7 chord on the flat 5 of the half diminished chord, in other words Abmaj7 to G7 to Cmin7. it is then a very small leap to make the Ab chord into a dominant 7th, so Ab7 to G7 to Cmin7. this occurs in How Insensitive. Bbmaj7 to A7b9 to Dmin7. and countless others as well. it happens somewhere in the 2nd 8 measures of stella by starlight too, depending on the changes you use. I got changes from Marc Johnson, he uses (last 4 before bridge one bar each) Fmaj7 Bbmaj7 A7b9 D7#9. so you can see that same movement there. also it kind of simplifies the changes compared to whats in the real book. easier to play on, and they still sound good and fit the melody (i think).

[Michael Case]

I would say that 1. the Ab7 is just the flat (minor 6th) in C min. It also serves as a secondary dominant (V7 of V7) to the G7. Functioning as a secondary dominant Ab7 is a tritone substitute for a D7, which would be the dominant (V7 of V7) of the G7.

If you're not sure how a tritone substitute works here is a quick explanation. In the tune "Equinox" the G7 is the V7 going to the tonic C-7. The Ab7 is a V7 going to G7. Ab7 works as a tritone because the Ab7 and the D7 (the V7 of G7) share the same tritone. The tritone is the interval that gives the dominant it's "pull" to the tonic. So the notes that make up an Ab7 are Ab, C, Eb, Gb. The D7 has D, F#, A, C. The tritone in Ab7 is C, Gb the tritone in D7 is F#, and C. F# and Gb are enharmonic names for the same chord. With the tritone staying intact the roots and fifths of those two chords are interchangeable. Also the root of the substituted V7 chord is a tritone away from the substitute V7 chord (D becomes Ab which is a flat fifth or sharp fourth which is a tritone).

You can find tritone subs in many standard changes. For example a ii, V, I in C major would be D minor, G7, C major. You could make it D minor, Db7, C major. The tritone in Db7 and G7 are the same F and B. In a G7 B is the third and F is the seventh. In Db7 the third is F and B (Cb) is the seventh.

Sorry if this is unclear or long winded.