Watch the Week 2: Theory on Tensions/The Art of Chord Substitution online guitar lesson by Bob Wolfman from Essential Guide To Jazz Blues Comping

Theory on Tensions/Chord Substitution -

In this lesson, we're gonna take a look at chord extensions, which are really just what they sound like they are. The prefix "ex" is usually dropped from the word extensions, thus the term "tension" remains. Chord tensions actually do create more harmonic tension within a chord itself. How does adding tensions to a chord happen? Well, we're basically extending the scale for whatever key a given chord is derived from, and then adding a tone or tones to that chord. People are often daunted by all the numbers associated with chords until they learn what they really mean and how simple a system chord construction really is. Everyone can count from 1 to 13, right? Well, that's the long and short of it and it all boils down to simple numbers assigned to the various tones in a scale in numerical order. Here is a list of guidelines to follow:

1. Tensions are upward extensions of the scale.
2. Tensions are non-chord tones (meaning they relate to the 2nd, 4th and 6th degrees of the scale). Remember, chord tones are the root, 3rd, 5th, and 7th degrees of the scale.
3. Tensions are added to chords to increase harmonic richness.
4. The usage and availability of tensions varies depending on the chord type. We refer to raised or lowered 5ths and 9ths as altered tones (or altered tensions).
5. Chord symbols with tensions are written in the following manner: C7#9 = C is the root - key 7 indicates dominant type chord #9 is an altered tension).
6. Altered Tensions - raised or lowered 5th's and 9th's are referred to as altered tensions; b5, #5, b9, #9, *NOTE - Tensions appear as a suffix written next to the chord symbol itself.
7. Using chords with tensions in place of the simple mother/parent chord is known as chord substitution. e.g., C7 = basic mother/parent chord. C7#9 may be substituted for the basic C7.