Can anyone shed some light on what makes this chord progression work?
I know that bVI is a common bit of modal mixture, and minor iv often replaces IV, but I'm wondering what makes them work together here.
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the flat 6 chord being a semitone above the 5 chord makes it work to "anticipate" it. In simple terms: chords a semitone above often work to resolve down. As a jazzer you can treat it as a tritone substitution if you like too, viewing the bVI as a substitution for a ii, but it's not really necessary. Another thing is that walking up from a major chord to the chord 1 minor 3rd above it is often quite a nice effect, it works sort of like changing that chord to a minor chord, but it's less stark and there's more movement. I bIII IV V for example, or I bIII bVI V – Some_Guy May 17 '18 at 4:13
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Also note that iv is the relative minor of bVI (or bVI is the relative major of iv). – No'am Newman May 17 '18 at 9:30
Like with anything else in music, follow the notes and the common tones and they'll tell you all you need to know. The basic idea that is presented in this progression combination of chromatizim though modal mixture along with the traditional resolutions we expect. Let's put a key to this progression. If we were in C major, this progression would map to C, Fm, A♭, and G.
- C - C, E, G
- Fm - F, A♭, C
- A♭ - A♭, C, E♭
- G - G, B, D
Notice that the C is common in all chords except the G which is taking you right back C chord and is approached by all notes moving down by half step. Also note while we are keeping C as a common tone, we are introducing other tones borrowed from the parallel minor which is adding a contrasting color to the progression. If you were to just move each note to the next closest tone, you would find this.
- C -> C -> C -> B -> C
- E -> F -> E♭ -> D -> E
- G -> A♭ -> A♭ -> G -> G
As you can see, two of the 3 notes don't move at all except moving away by half step and back. This if used effectively can create a lot of motion though use of chords not typically found in C major without actually having the notes move to far.
Chords that work together are found using the diatonic notes - C, Dm, Em, F, G Am and Bo. Also found to work are the chords from the parallel minor. So, Cm, Do, Eb, Fm, Gm , Ab and Bb. The chords in the sequence are C, Fm, Ab and G. All part of the previous lists.
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Then there's C#dim, which works very well between C and Dm. Or Ebdim which does the same thing coming down from C/E. Or Db7 which stands in well for G7. Or... just about anything else. It's really a bit silly making lists of what chords are 'allowed'. We can find a justification for any one. Sorry I keep implying that much 'theory' is rubbish. But it is! – Laurence Payne May 17 '18 at 16:39
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@LaurencePayne - it's all true. However, so many budding musos need parameters. So, to an extent, apart from attempting to explain the phenomena of what works with what, the 'theory' gives guidelines that are the crutch so many feel they need. Luckily, through the ages, most decent composers knew the 'rules', but had the temerity and bravery to go beyond them - won't necessarily say break them - some to their detriment, as their genius wasn't recognised in their lifetime, so accolades fell on deaf (or dead) ears. – Tim May 17 '18 at 16:51
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Good point for a student working on schoolroom SATB exercises. 'Stick to what Bach did for now - it's a coherent system that corresponds with a whole lot of real music'. But there seem to be rules in 'guitarist theory' that don't line up with any actual style of playing/composition/improvisation. Hence the continual queries here from people who want to know 'why this works' having found yet another real-world example that doesn't conform. – Laurence Payne May 18 '18 at 17:58
