here's the thing, a progression in and of itself means that there is direction; any other collection of chords is a sequence
Direction means that we would like to hear movement from chord I to chord V and back again to chord I (i-V-i is also included in this statement).
Cadences
Such progressions are based within cadence formulae
Perfect V-I G-C
Imperfect I-V C-G
Plagal IV-I F-C (similar to imperfect but differs in the functional position of the two chords involved)
Half-Close ii-V Dm-G
Interrupted V-anything but I or vi G-F, G-Em, G-Dm, G-Bmb5
Deceptive V-vi G-Am
Possible progressions
Common movements include
I-vi-ii-V-I-V-IV-I ~ C-Am-Dm-G-C-G-F-C
I-IV-ii-V-I-IV-V-I ~ C-F-Dm-G-C-F-G-C
I-iii-vi-ii-V-I-V-I ~ C-Em-Am-Dm-G-C-G-C
These are based on the idea that for some of the time each chord is followed by the chord that is a 5th away
Progression | 1st | 2nd | 3rd | 4th | 5th | 6th | 7th | 8th |
I-vi-ii-V-I-V-IV-I | - | m3 | p5 | p5 | p5 | p4 | M2 | p4 |
I-IV-ii-V-I-IV-V-I | - | p4 | m3 | p5 | p5 | p5 | M2 | p5 |
I-iii-vi-ii-V-I-V-I | - | M3 | p5 | p5 | p5 | p5 | p4 | p5 |
Cycle of 5ths
by extension then we can use the cycle of 5ths to provide even more direction, and even use subversion (short-circuiting or skipping parts) of the cycle to create directed progressions
The cycle of 5ths is the key to understanding the range of possibilities
I-IV-viib5-iii-vi-ii-V-I ~ C-F-Bmb5-Em-Am-Dm-G-C
looking closely at the 3 progressions above it can be seen that the cycle has been subverted in each (shown in parentheses())
I-(IV-viib5-iii)-vi-ii-V-I ~ C-(F-Bmb5-Em)-Am-Dm-G-C
I-IV-(viib5-iii-vi)-ii-V-I-IV-(viib5-iii-vi-ii)-V-I ~ C-F-(Bmb5-Em-Am)-Dm-G-C-F-(Bmb5-Em-Am-Dm)-G-C
I-(IV-viib5)-iii-vi-ii-V-I ~ C-(F-Bmb5)-Em-Am-Dm-G-C
Analysing these same progressions in terms of the cadences in play we get
I | vi | ii | V | I | V | IV | I |
- | half-close | imperfect | plagal | | | | |
- | perfect | interrupted | - | | | | |
C | Am | Dm | G | C | G | F | C |
I | IV | ii | V | I | IV | V | I |
perfect | half-close | perfect | perfect | | | | |
- | perfect | interrupted | - | | | | |
C | F | Dm | G | C | F | G | C |
the perfect cadence from I-IV is based on the idea that there is a temporary shift to the sub-dominant major (key based on Chord IV) where chord I is temporarily chord V and chord IV is I......
I | iii | vi | ii | V | I | V | I |
- | | perfect | perfect | | | | |
- | half-close | imperfect | - | | | | |
C | Em | Am | Dm | G | C | G | C |
Substitutions
then moving on to substitutions (rel major/minor, parallel major/minor, tritone, elisive (3rd above or below), chord tone sub (replace with the chord built on the 3rd or 5th of the chord), secondary dominants) for some chords via the subversion process and we can create progressions that have strong direction and movement
for example taking the 3rd of the progressions above, we can apply the following substitutions
I-V-I-IV-V-I-V-I ~ C-G-C-F-G-C-G-C
I-iii-IV-ii-V-I-V-I ~ C-Em-F-Dm-G-C-G-C
I-viib5-IV-ii-V-I-V-I ~ C-Bmb5-F-Dm-G-C-G-C
I-iii-vi-bVI-V-I-V-I ~ C-Em-Am-Ab7-G-C-G-C
I-V-of-vi-bIII-ii-V-I-V-I ~ C-E-Eb7-Dm-G-C-G-C
I have written in greater detail about these ideas elsewhere on fp