Tensions, also known as “extensions” and various other terms regionally, are the color tones added to basic chords, giving them modern harmonic flavor. Tensions have an air of mystique about them. They are regarded by many younger players as complicated and time-consuming to learn. Many guitarists learn these chords by pictogram and tab, and that’s okay, but I’m going to present a more in-depth method. The good news is that this information is easy to understand, and you can implement it right away. You will be able to construct any type of “advanced jazz” chord by learning this material. Of course, though the rewards are worth it, you’re going to pay some dues to really get inside this material. It takes time and patience.
Let’s start out by defining what a tension is: a tension is a tone that adds color and discord to a chord without confusing the quality (type) of the chord. This simply means that while you embellish it and make it sound more modern, etc., the chord is still recognizable as being major, dominant 7, minor 7♭5, or whatever.
Probably the best way to study the use of tensions is by period. You can study periods in jazz harmony (and use of tensions) almost by decade, and we’ll be focusing our attention in this chapter on jazz harmony between 1930 and 1960. But rest assured, this material is alive and well and very much a part of present jazz harmony. It is essential language in the study of jazz guitar and an important part of all practical jazz guitarists’ knowledge base.
Tensions can be applied to harmony both vertically and horizontally. This means that on a given chord structure, we can add the tensions on top of a chord or in place of one of the basic chord tones. This is vertical thinking: the chord tones and tensions sound simultaneously. Horizontal harmonic thinking about tensions is basically scale oriented. The pitches of a scale can be harmonized with notes of that scale, resulting in diatonic harmonies and tensions. These harmonized scale voicings create tension and release as one moves horizontally through the harmonized scale’s harmonic structures. More commonly known as “comping by scale,” this method of generating harmony was widely adopted by Bill Evans, McCoy Tyner, Chick Corea, Herbie Hancock, and many others in the late 1950s and 1960s (see chapter 6).
Our goal here is to upgrade the basic harmonies that are generated by tertian thinking (harmony built by thirds) as opposed to the quartal harmony (harmony based on fourths) so indigenous to comping by scale sounds of the 1960s. However, sometimes converting the closed harmony to open, and then adding tensions, creates intervals of fourths in a chord’s makeup.
* Tensions applied vertially by chord: tertian harm ony . (Notice the fourths in the chords.)
b.**
** Tensions and chord tones m oving horizontally : quartal com ping by scale concept. Fig. 5.1. Tertian and Quartal Voicings
You’ll notice in figure 5.1 that the vertical-tertian chords have quite a few fourths in the chords. The addition of the tensions and the respelling of the G7(♭9,13) and C6(9,♯11) chords have resulted in some intervals of a fourth in the construction of the voicings. So, is it a fourth chord, or a tertian chord? Viewed from a construction standpoint, they have elements in common but are still tertian. In the end, tertian vs. quartal thinking is just an orientation. The final result, musically, is what counts. Sometimes musical theory produces situations that can be analyzed in more than one way, but the final judge as to its relevance is your ear. Jazz compers mix tertian and quartal voicings together freely!
It's easy to see the thirds orientation in (a). In (b), the respelled chord still has som e fourths (an augm ented fourth, a perfect fourth, and a dim inished fourth), even though we're "thinking" in thirds. Fig. 5.2. (a) Thirds vs. (b) Fourths
Since we’re thinking about tertian chord theory in this chapter, consider a list of tensions as they relate to the primary seventh chords that are built in thirds. A word of caution! This is a sonority-based system where the tension is used on particular chords just because it sounds good. These are “common practice” usages that are drawn mainly from the so-called “hard-bop” period (1950s). This is a different orientation from basic chord-scale theory that draws available tensions from primary diatonic scales. Some of our “sonority based” tensions violate “function intent” rules, and/or would be considered “non-diatonic” in some cases of harmonic analysis. So be forewarned; some of the tensions that we’ll use here would be considered “wrong” or “unavailable” in more academic settings, at least in the more primary applications.
One additional thought: Any note can be added to any chord to achieve a desired musical effect. The listing of tensions for these particular chords is the way that Joe Pass, Wes Montgomery, Tal Farlow, and others might color a chord. But, if you wanted to go a little more in Thelonious Monk’s direction, or if you were writing a score for a movie that called for some shocking sounds, you could deviate from the chart. Remember, these sounds (tensions) are a place to start from. They’re in the tradition and will help you get good results musically. You need to listen to players from all periods to understand the history of usage.