Altered Scale Minor 3rd Transpositions

A guitarist on the forum of Dave Stryker’s class at Artistworks recently asked an interesting question that really piqued my interest. The question is, can you transpose the altered scale in minor thirds, the same way you can transpose the diminished scale? I’ve been thinking for a while about how the diminished, altered, and whole-tone scales are related, so let’s treat this as a prelude to that topic.

The altered scale differs from the diminished scale in two ways. First, the altered scale is a seven-note scale and the diminished is an eight-note scale, so the altered will always have one note missing compared to the diminished. Second, the altered scale has one note different, it has a b13 (or #5), where the diminished scale has a natural 13. So, to sum up, one note missing, one note different. You can see this in the first figure.

Comparison of the altered scale and the diminished scale
Figure 1. Diminished Scale vs. Altered Scale

(Note: in the figure above, the Arabic numbers in the second row are called pitch classes. If you are not familiar with them, for now, you can assume 0=C, 1=Db, 2=D, and so on. It is much easier to think about transpositions, inversions, and symmetry when you consider pitches this way.)

Now lets see what happens as we start transposing at minor 3rds. For the altered scale, as we already know, every time we transpose a minor 3rd, we end up with the same collection of pitch classes, so essentially the same chord and the same extensions. Check out what happens with the altered scale. For each transposition, we have one note missing (the last column) and one note different (highlighted in yellow).

Comparison of the altered scale and the diminished scale, showing transpositions at the minor third.
Figure 2. Diminished Scale vs. Altered Scale m3 Transpositions.

Of all the transpositions of the altered scale, the one at the tritone makes the most sense; it’s easy to see it as a dominant 13 #11 chord. The other two minor 3rd transpositions are maybe a little trickier, since one lacks the major 3 and the other lacks the seventh. But I would wager that one could make convincing use of all of the transpositions, and maybe sound a little bit outside.

Here’s the same figure with pitch notation rather than pitch-class notation.

Comparison of the altered scale and the diminished scale, showing transpositions at the minor third.
Figure 2. Diminished Scale vs. Altered Scale m3 Transpositions (with traditional pitch notation).

One more thing I’ll point out, and this is admittedly getting into theory-geek territory. Since the diminished scale is an eight-note scale, it has four notes missing with respect to the twelve-note chromatic scale. In the language pitch-class set theory, those four notes together form the complement of the diminished scale; diminished plus complement equals chromatic. You will notice that the highlighted different notes in the altered scale, taken together, for the complement of the diminished scale. I’m not sure if that is a useful observation in jazz, but if Anton Webern played jazz, he would probably have figured out how to use it.

Quartal Harmony: Tetrachords

In today’s post we will continue our series on quartal harmony with a quick look at quartal tetrachords. When we began with dyads, we saw there are three quartal dyad types: P, A, and D. With quartal trichords, there are nine types (3 * 3). With quartal tetrachords, we now have twenty-seven types (3 * 3 * 3). These are summarized in Figure 2. Of the twenty-seven, only eleven occur in our four scale harmonizations.

As before, the most common tetrachord type is based on stacked perfect fourths, PPP. This type occurs nine times in total across the harmonizations, making it once again the most harmonically ambiguous chord type. PPP occurs four times in the Major harmonization, twice in the Melodic Minor, and once in each of the other harmonizations.

After PPP, the next most common tetrachords are PPA and APP, both of which occur four times, once in each of the harmonizations. Both of these are very useful voicings. APP can easily serve as a Maj7#11 and PPA can serve as a dominant, as we shall see next.

When looking across the four harmonizations, we see an interesting detail on the both the supertonic and dominant degrees: they each share the same tetrachord across the harmonizations. In all cases, the supertonic is a PPP, and the dominant is a PPA. In other words, the II-V quartal tetrachords are the same for Major, Melodic Minor, Harmonic Minor, and Harmonic Major.

We mentioned the Viennese trichord in our last post. Any tetrachord that contains either PA or AP is a superset of the Viennese trichord. Our next most common tetrachord is PAP, which occurs three times in the harmonizations. Once can see PAP as an interlocked PA and AP, or an interlocked Viennese trichord. A Viennese tetrachord perhaps? This voicing also functions well as Maj7 11 chord.

Quartal tetrachords harmonized with the major, melodic minor, harmonic minor, harmonic major scales.
Figure 1. Major, Melodic Minor, Harmonic Minor, Harmonic Major scales harmonized with Quartal Tetrachords.
Quartal Trichords in scale harmonizations.
Firgure 2. How many times does each tetrachord appear in the four scale harmonizations?

Key Takeaways

From a practical standpoint, here are a few things to keep in mind using quartal tetrachords for comping or soloing:

  • The texture of a quartal tetrachord is getting fairly thick and might be a practical upper limit for comping, especially on guitar
  • The quartal tetrachord material for II and V is the same for each of the four scales, so work on those quartal II-Vs and you will get a lot out of them!

Quartal Harmony: Trichords

Today we continue the discussion on quartal harmony with trichords. Yesterday’s topic on quartal dyads was a bit of a warm-up. Things are getting more interesting now. There are three varieties of fourth: perfect, augmented, and diminished, or using our labels, P, A, and D. In order to construct a trichord, we need two intervals. That gives us a total of nine different types of quartal trichord. These are shown in the Fig. 2 chart below. When looking at the harmonizations of our four scale types, Major, Melodic Minor, Harmonic Minor, and Harmonic Major, we can make some observations about how often the trichords appear.

Two of the trichords, AA and DD, do not appear in any of the harmonizations. In AA, the outer voices form an augmented seventh, which is enharmonically equivalent to an octave. In DD, the trichord is enharmonically equivalent to an augmented triad.

We saw yesterday that P was the most common dyad, and see now that PP is the most common trichord. It occurs five times in the Major harmonization, three times in the Melodic Minor, and two times in each of the Harmonic Minor and Harmonic Major. So then, just like the P dyad, the PP trichord is the most harmonically ambiguous of the quartal trichords.

The next most common trichords are two of my favorites. They combine an outer major seventh, and inner perfect and augmented fourths, or PA and AP. I love both of these sonorities and used them often in my early composing. (Berg and Webern loved them too, so much so that they are sometimes referred to as the Viennese trichord.)

Two of the trichords occur in only one harmonization. PD occurs in only the Harmonic Major harmonization, and DP occurs in only the Harmonic Minor. As a result, these two trichords are the most harmonically specific.

I find it interesting to look at the similarities and differences among the four harmonizations. One thing that leaps out is that all four harmonizations share the same trichords on modes 1, 2, and 5, or on the tonic, supertonic, and dominant. So, for example, a riff on the tonic and supertonic trichords would be completely harmonically ambiguous; it would fit with any one of the four scales. Somewhat surprisingly, the dominant is the same for all four.

Not surprising is where the most variation occurs between the harmonizations: on the mediant and leading tone. Both of these degrees (or modes) contain both the third and the sixth, which is where all of the variation between these four scales takes place. Contrast this with the subdominant and submediant. The subdominant trichords contain the third, so the two with the lowered third are the same, and the two with the natural third are the same. For the submediant, the two with the lowered sixth are the same, and the two with the natural sixth are the same.

Quartal trichords harmonized with the major, melodic minor, harmonic minor, harmonic major scales.
Figure 1. Major, Melodic Minor, Harmonic Minor, Harmonic Major scales harmonized with Quartal Trichords.
Quartal Trichords in scale harmonizations.
Firgure 2. How many times does each trichord appear in the four scale harmonizations?

Key Takeaways

From a practical standpoint, here are a few things to keep in mind using quartal tichords for comping or soloing:

  • The texture of a trichord is very useful for comping, especially on the guitar
  • Any quartal trichord material built on I, II, and V will work for each of the four different scales
  • The quartal trichord material on II, VI, and VII is where all the harmonic differences are

That’s it for today’s installment. In later posts, I will look at quartal tetrachords, as well as usage of inversions for the trichords we looked at today.