Chord Substitution

Remember harmonizing scales both major and minor? If not review them.

What I didn't mention before is that those chords can also substitute cleanly for each other, therefore if you see an Dmin7 in the key of C you can easily put an Fmaj7 there (this applies to both comping and soloing aspects) since these chords are so similar. This can completely alter a lot of chord progressions, let's take a three chord rock.

C | C | F | G

Change that to:

C | Em | Dm | G

or

Am | C | Dm | Bdim7

the possibilities are huge, your soloing will be coloured up as well by super imposing these chords over top of the base progression.

However it's only one note difference right? Not that big a deal? Now let's combine that with tritone subs and secondary dominance. I'll begin using 4 note chords just to visualize this better, the seventh can easily be stripped to give a more rock based sound.

Cmaj7 | Cmaj7 | Fmaj7 | G7

Now let's put a iii chord into the second measure using like function.

Cmaj7 | Em7 | Fmaj7 | G7

Now let's add ii-V based off that Em7 using secondary dominance.

Cmaj7 / F#m7 B7 | Em7 | Fmaj7 | G7

Now let's use a tritone sub over that new B7

Cmaj7 / F#m7 F7 | Em7 | Fmaj7 | G7

Now let's use a like function sub from that F#m7 – it's currently the ii chord, so let's make it the IV chord of E.

Cmaj7 / Amaj7 F7 | Fmaj7 | G7

Now let's use a like function sub over that Fmaj7 chord

Cmaj7 / Amaj7 F7 | Emin7 | Dm7 | G7

The same type of ideas can turn this simple progression into some really bizarre harmonies, the possibilities are near endless, any attempt to list them all would be pointless, it's necessary to understand the concepts.