How do you justify the progression of a chord progression?

[Bob]

Generally, you have the home-tonic-stable chords, predominant, dominant, and then "filler" chords.

How do you justify the motion though?  Like from ii V or IV V?  Why is it that ii or IV are "pulled" toward V?

[Bob]

Come on..... come on.....

[Bob]

ii and IV have steps 4 and 6 in common.  Those both want to move to step 5.


For V I   (haha... sounds like IV V I, anyway...)  For V I, step 7 and 2 want to go to step 1.  Step 5 in already in a tonic chord.

[Bob]

what are you thoughts?

(Bob calls on Faulty Damper.  "Yes?... Yes, you.  Go ahead.  What are you thinking?"  )

[Bob]

I'm right here, waiting.   (taps foot, drums fingers)


There must be something to the falling fifths progression.  The third and fifth moving to the next root.  The root of the original chord being a common tone in the next chord.

But why does the IV V progression work?   VII I seems similar. 

I suppose I could do a search too....

[faulty_damper]

Because of the voice-leading =  It just so happens that it avoids parallel 5ths and 8vs in these movements, which sound bad.  Also, iii contains two common tones with V (lack of motion), vii is diminished and doesn't sound like it wants to go there, and vi contains two common tones with the tonic, which doesn't really sound that great to V.

This works for just about anything.  If you really wanted to, you don't even have to look at the roman numerals, just move the voices paying close attention not to have parallels 5+8s and be sure to resolve leading tones.  If you do it this way, you'll end up creating very fanciful harmonies that sound pleasing.  You could then add roman numerals to it to see what you have created.

Even children who compose will know to avoid parallel 5ths and 8vs, not because they were told it but because they sound bad.  They also know to resolve leading tones because it sounds bad if they don't resolve it.  They also will understand that if they move all the voices, it can sound bad and they learn that they can keep common tones to keep it sounding good. 

If they are taught with rules and not by their own aural experiences, they'd never understand harmony which is pretty much the situation with most music students in universities and conservatories!

How do you justify the motion though?  Like from ii V or IV V?  Why is it that ii or IV are "pulled" toward V

There are many ways to justify it, but only one way that is universally accepted but not never actually taught.  It just sounds good!  If you try any other chord, it probably wouldn't sound as good in diatonic harmony.  (In chromatic harmony, you can actually have many different predominant chords becuase many options are created when you add chromaticism (all paths lead to Rome kind of deal) but voice-leading principals still apply.)

[Bob]

Because it sounds like it's increasing the tension.  It sounds like it's moving forward.....

[Bob]

Thinks more....

In diatonic harmony  (btw, I don't count those chromatic V/V's as being predominant... I don't think.... At least not the viio's.  They just collapse into the chord anyway)


In diatonic harmony,

.....   "I'll be Bach!"....

[faulty_damper]

But then my previous reply still only responds by using theoretics...

The issue with the V is that it contains a leading tone.  If you start a diatonic scale and stop at the leading tone, it sounds terrible...  Resolve it already!  This scale example implies harmony with just the melody.

How to get to V? Why not just I - V - I?  It sounds good... but it doesn't sound interesting!  So add something between I and V.  It's easy to experiment: You only have five choices of chords.  Go to the piano and play I - the five other chords - V and you'll have your answer.

But really, the thinking-man's answer alludes me... Why does a Dominant 7th want to resolve so badly?  Why do pianists still play the repeat in Chopin's Bb minor sonata, first movement at bar 5 where the dominant 7th doesn't ever resolve?  It resolves at bar 1, not 5...  Whenever I listen to this sonata and the pianist doesn't repeat at bar 1, I quickly fill in those missing bars before it repeats so I have a sense of resolution.  Ah,  that tritone has moved to the respective seats in the auditorium.

[faulty_damper]

The thinking man's answer would involve the study of the overtones and such.  I don't have a harmonograph (whatever that is).  And even if I did know, it wouldn't actually matter from an aural perspective.  It explains what we hear but not why we hear it the way we do.  But a harmonograph would look so much cooler than a bunch of words neatly arranged in a manner that people understand but actually don't since it's about abstract concepts.

[Bob]

Overtones... hmmm.....

The pull each step of the scale is part of the answer. 


(Bob groups diatonic chords)

I ii iii IV V vi viio

I, iii, vi   are the "resting/tonic" catelogy.  They have step 1 and 3 in common.  Really, step 6 could be added to a tonic chord and it's still not going anywhere.  Step 1 and 3 are basically tonic and still.  6 would have a slight pull, and that's toward step 5.  I, iii, and vi chords are a third apart.

ii, iv are in the predominant category.  They have steps 4 and 6 in common.  Again, for the iv chord, adding the 6th/step 2 really wouldn't change the function of the chord -- similar to a I+6 chord.

That only leaves... V and viio.  viio is really just an extension of V. 



Tonic -- predominant -- dominant --- tonic

And variations.  That's it.  If you put it vertically, it's like a ladder, a ladder of tension.



But why is there that progression, moving forward feeling?....  Individual note pull, overtones....   It always builds up to V and then release tension back to a I resting state.

Hmm.... still not happy with the answer.  This is just what happened in theory class too....

[Bob]

Basically a state of rest.  But that's boring, so you want to go somewhere.  In order to keep moving forward, you have to increase the tension.  Eventually, there's no more room for tension -- the V chord must be the most tense chord.  No where else to go, so it "bursts" and falls back down to where you started.  Is the dominant chord the most tense chord?  There must be different types of tension.  It's not the type of tension created by clashing of individual notes in a chord. 

[ted]

Actually Bob, I think your question is a very profound one, perhaps deeper than you intended it to be. Everybody has given the usual answer, that there exists a set of responses, more or less universal across all human brains. Because these responses are so widespread, sets of instructions have been developed over time to describe and generate them. As everyone has rightly pointed out, rules alone are no good unless we understand why they exist and what they purport to model.

All well and good, but I would go one step further and ask what happens if a given creative individual doesn't even understand the underlying part, the "why" of the matter. I am such a person and I cannot believe I am unique, that would be statistically ridiculous. Describing a "desire" or "necessity" to go from one particular note combination to another is like trying to tell me what it feels like to be blind, deaf, have absolute pitch, have one leg, be schizophrenic, have a baby or hundreds of other states which I have never experienced or am biologically incapable of ever experiencing.

These harmonic imperatives - desire to go from one particular combination to another - are NOT invariant across all human brains. I have tried to explain several times on forums but have more or less given up now. On Pianoworld I generated such antagonism, why I cannot imagine,  that I have altogether ceased discussing it there.

But that is a very, very good question, Bob, and I don't think its implication has fully sunk in yet.

[Bob]

Still thinking... There's the phenomena of having a tonal center too.  That's another element.

[prometheus]

I wouldn't have used the world 'justify'.

Also, read Schoenberg's book on harmony. It deals with those questions.

[Bob]

Maybe "Why does it work?"  or "How does it work?"

I was just browsing through the Schoenberg book earlier this summer.  I should go back and check.