Here is a quick little demonstration of some reharmonization that you might enjoy. Yes, I know that it is July, but I am going to use the song “Have Yourself a Merry Little Christmas.”
I am going to be changing chords, but don’t look at it as chord substitutions. I am actually going to be changing chord progressions.
Here are the first two phrases from the song with traditional harmony.
I want you to notice the boring chord progression (I – V) that happens in each phrase.
How do you change a I – V progression into something more interesting? One solution is to change it into I – iii – (flat)iiidim7 – ii – V7(b9).
There are very logical reasons that this works that I will go through quickly. First of all, in the first measure, I am changing the C chord to a progression (C – Emin7 – Ebdim7). It is very common to substitute a progression of chords for a single chord and it sounds great as long as progression moves in a functionally correct way and leads nicely into the following chord.
Why did I choose these chords? First, the Emin7 works because a iii chord is functionally equivalent to a I chord. So that one is a straight substitution.
The Ebdim is more tricky. That chord is actually also a substitution–for a A7. A7 (VI7) would be a logical place for Emin to resolve to because it is down a fifth. But I happen to know that a (flat)iiidim7 substitutes beautifully for a VI7 chord for certain melody notes.
The second measure is G7. I am going to substitute a progression consisting of Dmin7 – G7 instead. Doing a ii7 – V7 substitution for a V7 chord is something I do constantly.
So, when you put both of those substituted progressions together, you end up with one progression that works functionally. Here is how I might play it.
What is the takeaway? Start thinking about progression changes rather than chord substitutions. Learning to replace V7 chords with ii7 – V7 progressions will by itself help your music dramatically.