Theoretical Explanation
The theory behind it is these chord movements create notes that will move forward or
ascend in the scale. To illustrate, I’ll use some examples in the key of C major.
Up a 2nd: For C major to D minor, each of the notes in the C major chord move up to the next note in the scale for the D minor chord.
C major = C E G
D minor = D F A
C --> D (moves up)
E --> F (moves up)
G --> A (moves up)
Up a 4th: For C major to F major, there are two notes in the C major chord that move up to the next note in the scale for the F major chord. The C note is in both chords, so there is no movement from the C note.
F major = F A C
C --> C (same)
E --> F (moves up)
G --> A (moves up)
Down a 3rd: For C major to A minor, only one of the notes moves up to the next note in the scale and the other two remain the same.
A minor = A C E
C --> C (same)
E --> E (same)
G --> A (moves up)
As mentioned above you can see how all three of these movements have notes that progress forward in the scale... That is why they sound like they are moving forwards. The I IV V I progression works so well, because it uses these conjugations and the progression always sounds like it is moving forward.
I to IV is up a 4th
IV to V is up a 2nd
V to I is up a 4th.
Any progression you make using these three movements will sound similar to the I IV V I progression in that it will sound like it is moving forward or “progressing”... This gives a new meaning to the term “chord progression”.
