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Old 08-28-2017, 12:08 PM
JonPR JonPR is offline
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Originally Posted by OliveCorduroy View Post
Hello all,

So in keeping with a few other posts that I have made about chord progressions, with one of them being 'what are some common chord progressions', I have a related question.

I have been playing some of the progressions suggested to me and it got me thinking that there has to be some rules(for lack of better word) that determine which chords are better suited to precede others and which ones are better suited to follow another and while others are not allowed(again, for lack of a better word).

Going into this question, I recognize that this is all about music theory and I want to dig into that but I don't even know where to begin. I understand the major scale and how chord progressions are developed from that but other than that I don't know why some work well while others don't.

Any comments would be great.

Thanks,
George
There's two basic principles, from which all the others arise:

1. Key (or mode)
2. Voice-leading

Key (or mode) is not just about chords being drawn from the same scale (pitch collection), but sharing a sense of tonal centre. Obviously, if chords all come from the same scale ("diatonic") they will sound related whatever order you put them in. A lot of rock and pop is built on this simple principle.

The question of "cadence" is another matter, and refers to how chords can be made to "progress" from one to another, and "come home" at certain points. I.e., not only are you aware that the chords share a key, and that there is a keynote, but you can hear the movement towards that keynote - you know when it will arrive by how the chords leading up to it are arranged. (This is the "circle progression" I mentioned in that other thread.)
Jazz - at least the jazz standards of the first half of the 20th century - loved this principle of "functional progression", leading the ear this way and that; sometimes surprising you with a swerve - and often going out of key - but always logically, and always coming home in the end, in a fairly predictable way.
Rock, pop and R&B is less bothered about that "forward movement", about harmonic tension and release. It's happier with open-ended grooves and weak cadences (if any). This makes it more "modal" in spirit, like the blues and folk music which largely gave rise to it.
But both genres share that sense of allegiance to an overall key. A home point to start and end on.

Voice-leading is the actual mechanism by which all chord changes work. This is a principle which is best summed up as economy of movement between chords.
Imagine you have a choir - it could be four voices (for Bach chorales or any sequence of 7th chords), or it could be six (one for each guitar string, even though you rarely need all 6).
This choir is a very lazy choir (except for the bassman, but I'll come to him). They really like to keep singing the same note if they can, as the chords change. If they can't do that (if the chords won't let them) then they want to move to a note that is a half-step or whole-step above or below; no further than that, please. And they also slightly prefer descending moves to ascending ones, if that can be arranged (descending is so much more relaxing...).
The bass is a little more energetic. He doesn't mind jumping up and down between chords at least if he's been given the root job. But he's also partial to scalewise moves, especially descending.

Voice-leading is particularly evident in circle progressions using 7th chords, as shown in most jazz tunes. Look at this sequence:
--8---8---7---7---5---5---3---------------------------
--8---7---7---5---5---3---3-------------------------
--9---7---7---5---5---5---4-------------------------
--7---7---5---5---5---4---5----------------------------
------------------------------------------------
------------------------------------------------
Sweetly predictable, right? Mellow and cheesy? Especially the final settling on the G triad (bor-ing). The point is to see how this sound is achieved. Every "voice" (there are 4 here) either stays on the same note or descends by a scale note (half or whole step). Its cheesiness is mainly down to it all being diatonic (G major scale). Nothing to frighten the horses here.

Now try this:
--8---8---8---8---6---6---5---5---4---------------------
--8---8---7---6---6---5---5---4---4-------------------
--9---8---8---6---7---6---6---5---4-------------------
--7---7---7---6---5---5---4---3---2----------------------
------------------------------------------------
------------------------------------------------
More surprises there, right? Chromaticism, key changes (maybe), secondary chords or substitutions. And yet it all works - because the voice-leading mechanisms are all solidly in place. (I could have put an ascending move or two in there, but decided against it.)
I only cheated slightly, by giving each pair of chords a familiar functional relationship. And each chord is a standard 7th type. (I could have thrown a few weird alterations in.)

The point here is you don't have to put whole strings of chords together like this. The voice-leading principle means you can throw an odd chromatic chord into a sequence if (a) it shares a note with the previous chord (and ideally with the one after), and (b) one of more of its other notes is a semitone move.

IOW, voice-leading over-rides diatonicism (shared scale) and functionality (ii-V-I cadences etc).

At least up to a point... It's possible to go too crazy with this idea, and the ear eventually demands (IMO) some kind of return to a tonal relationship between the chords. A roller-coaster is all very well (the voice-leading is what keeps it on the rails), but you (probably) want it to settle down to a nice straight level bit at the end.

BTW, chords don't have to move smoothly like that. Sometimes you want a voice (sometimes a whole chord) to jump more than one note - for dramatic purposes. That's where MELODY comes in. Melody is the elephant in the room here (a pretty one, but still an elephant...). Chords should always follow a melody. The melody is in charge. No good messing around with all those fancy chords if they derail the melody. (Sorry, you're now getting an image of an elephant on a roller-coaster....) Melodies, of course, are free of those voice-leading strictures; the singer of the melody is not one of those lazy choristers. The melody will often jump huge steps (yep a pretty athletic elephant), but sparingly - jumps cause tension, which then needs releasing by smaller moves, usually in the opposite direction (I think that elephant is on a trampoline now...) When one voice jumps (melody or bass), it's usually best for the others not to, but to balance it in some way. But - as always in music theory - the "rules" are not laws; they're just "common practices".
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Last edited by Kerbie; 08-29-2017 at 12:16 PM. Reason: Removed masked profanity
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