The most common chord progression in jazz music — as well as many pop songs — is the ii – V – I chord progression. For many beginning guitar players, this topic can be a little bit mystifying so let’s unpack it.
In every major key, there are seven chords. Regardless of which key we are in, the quality (major, minor, diminished) and the order in which they occur will never change. Here’s an in example in the key of C major.
C, Dm, Em, F, G, Am, Bdim
As mentioned, the quality and order of these chords won’t change, so they are not exclusive to any given key, so we can begin to represent them as numbers rather than specific chords symbols:
1, 2m, 3m, 4, 5, 6m, 7dim
Now, let’s switch to the commonly used format of Roman Numerals:
I, ii, iii, IV, V, vi, viidim
So a 2m, 5, 1 (also written as ii, V, I) in the key of C major is created with the following chords: Dm, G, C. Let’s do another on in the key of G — Am, D, G. Easy, right?
So … what’s the big deal?
You may be saying “I’ve played all of these chords before, and probably in this order. Who cares?” Well, this specific chord progressions occurs extremely frequently, and within this specific cadence lies a hidden world of harmony for us to explore. Let’s get started.
Scales, Arpeggios, and more scales
If the the three chords in question are all derived from the same scale, you could simply run up and down that parent scale for a solo or to create a melody, and that would certainly work — this is sometimes called “playing above the changes.” However there is a different approach that is more interesting — it’s called playing “inside the changes.”
The idea is to use the notes in the scale deliberately and with intention; instead of just playing the C major scale up and down, use the notes of any given chord at that moment (arpeggios).
Once you’ve master the parent scale and the arpeggios, you can then begin experimenting with different scales other than the C major scale and it’s modes. For example, try playing the G whole tone scale or the G half-whole diminished over the V chord. And endless array of new sound are possible, so open your ears and dig in!