Tri-tone Subs & Minor Third Subs

Hey Jazz Guy…

What can you explain tri-tone subs, and minor third substitutions? Im trying to make my chord melodies more interesting, and what’s the purpose of this technique? — Sub-Par in Salt Lake

Dear Sub-Par:Well, the purpose of the tri-tone sub, or any reharm technique, is to create the un-expected for the listener. We all have certain things we expect to hear in any situation, so by changing the chords, we are ‘awakened’ to a different way of hearing. This is the philosophy behind reharm in my opinion. NOW…on to the details. How do we create this? Well the tri-tone sub is great because it doesn’t deviate too far from the original chord (as the guide tones are the same), it just changes the bass note, and reverses the tensions. So this tends to give a very smooth effect, as opposed to merely playing the 4th root motion. The minor third substitution is a little more complex.

This involves the concept of modal interchange. This means that, say in the key of C major, you can substitude any chord that is diatonic to another mode of C, like C minor (Eb major), C Phrygian (Ab major), C Dim. Ect. In effect, this gives you ‘access’ to dozens of chords that would otherwise be completely random. THEN what you can do is to turn these chords into ii-V progressions as well. For Example:

D-7 Bb-7 Eb7 (from C Phrygian), G7 Cmaj7.

Or going even further:
D-7 Eb-7 Ab7 (from C Locrian) G7 Cmaj7.

To get these to the point where they don’t sound forced takes a lot of practice and a lot of experimentation. There is no way you will use all the possibilities all the time. In fact, I would encourage you to pick two or three that you like the most and play them through in every key. Then see if you can imply these ‘extra’ chords in your soloing, even when they are not there. Once you’ve got it, you’ll see you have a beautiful unexpected effect to pull on the listener at your command. Its kinda sexy…