I would like to know few things about chord progression

Question

I would like to know few things about chord progression:-

(I-IV-V) (I-III-IV-V) (I-II-V-I) (I-IV-II-V-I) (I-VI-II-V-I) (I-III-VI-II-V-I)

These are some of the popular chord progressions.

1. What is the logic behind these chord progressions?? why I IV V?? is it because of circle of fifth ?? or some sort interval? How did the musicians came up with this?

2. How are these chord progression played in a song? is Chord I played first then IV and V -and the same pattern continues?? or these chords can be played randomly??

I am completely new to music, and was wondering how all this stuff works, though I know how to construct triad and seventh chords. I also know that in a major scale I IV V are Major chords, II III VI are Minors and VII is a diminished.

I'll be happy if someone could explain me all this, I tried finding it on the internet, but it was all in vain.

Thanks for your time

Answer 1

The chords of the major scale are I ii iii IV V vi viio (Upper case = Major; Lower case = minor; Lower case with o = diminished).

Each one of those chords has a certain tension - ranging from none (I) to very tense (viio). That tension depends on the notes of the chord (how many notes it shares with the I chord and whether or not it has a leading tone):

• I consists of 1-3-5, and is the most stable chord.
• ii consists of 2-4-6: No notes in common with I, doesn't have a leading tone.
• iii consists of 3-5-7: 2 notes in common with I, has a leading tone.
• IV consists of 1-4-6: 1 note in common with I, doesn't have a leading tone.
• V consists of 2-5-7: 1 note in common with I, has a leading tone.
• vi consists of 1-3-6: 2 notes in common with I, doesn't have a
  leading tone.
• viio consists of 2-4-7: No notes in common with I, has a leading tone.

There are also differences based on which notes are in the chord, as 1 is more stable than 5, 3 and 5 want to move to 1 but are stable, 2 and 7 want to move to 1 and are unstable, 4 wants to move to 3, and 6 wants to move to 5, but those differences are subtle, so we won't discuss them - just be aware that they are a thing.

We could also categorize those chords into 3 different groups based on their tension: Tonic (stable), Subdominant (some tension, doesn't have a real strong sense of resolution when resolved) and Dominant (tense, has a strong sense of resolution when resolved. I iii and vi are T, ii and IV are SD and V and viio are D.

In functional harmony, T can move to SD or D, SD can move to T or D, and D can move to T. So in all of those progressions, we can see that kind of movement:

• I-IV-V = T-SD-D
• I-iii-IV-V = T-T-SD-D
• I-ii-V-I = T-SD-D-T
• I-IV-ii-V-I = T-SD-SD-D-T
• I-vi-ii-V-I = T-T-SD-D-T
• I-iii-vi-ii-V-I = T-T-T-SD-D-T

And for your other question - There isn't a rule about how long a chord should last, it can last a beat, half a beat, 4 beats and so on... But mostly when talking about pop songs which are usually going to be in 4/4, it will probably last 4 beats (a measure).

Answer 2

By listening to many pieces, you will understand that while any chord can and does follow and precede any othe chord in a diatonic piece, certain tried and tested patterns occur time and time again. Check out '12 bar blues' as a format that never seems to fail!

You asked about I IV V. Put simply, I is the home chord, analogy - where a journey starts. A very common, because it sounds acceptable to us, change is up a fourth. So a chord that can follow I is IV. Now, we're about as far from I as is possible. How to get back? Use the fourths trick again, and this time, the jump is a fourth from V to I. We're home again. That's a very short journey, but it's taken us from home, back again, in a natural sounding way.

Any of the diatonic chords will fit anywhere, but some do sound more like they're meant. Take the jazz 'ii>V>I. That again uses the moving a fourth. In C, ii is Dm, up a 4th to G, up another to C. So, so common. It also works with non-diatonic chords. In C, play a bar of E (maj), up 4 to A, up 4 to D, you can see where it's going to end!

Use your ears, and try any diatonic chord followed by another. You'll very soon hear what sounds good and not so good. The 'rules' are based on these premises. Incidentally, Roman capitals usually represent major chords (with a maj 3), while lower case show minors. The dim is lower case as it has that m3 also.