5.8Tonic substitutions

Play:

C → F → G7 → C

Now replace the first C with Am:

Am → F → G7 → C

This still works.

Or:

Em → F → G7 → C

Also works, though with a different color.

So tonic-family chords can create variation.

A useful first model:

Tonic family: I, iii, vi

Not absolute law, but a very good practical starting point.