Fun With Triad Cycles

Ex. 4 Triads Pivoting Within a Major 10th

My teacher, Mark Sherman, gave me a simple assignment at our last lesson: practice cycling through 12 keys using only major triads, mostly as 4-note chords, all while restricting yourself to a narrow range. I think this one is worth dedicating some serious time.  

OK, so let’s think about this algorithmically. The basic rules are simple: 

  • The only notes allowed are from the major triad 
  • Play 4 notes from each triad
  • Keep going in the same direction until you hit an upper or lower boundary, at which point, change direction 
  • No repeated notes 
  • After 4 notes, cycle to the next triad in the descending cycle of 5ths 

First question: what is the most narrow range into which you can fit the entire cycle? Answer: ok, maybe a bit of a trick question? Obviously, you need all 12 notes, so the smallest range would be 12 semitones, or a major 7th. Another obvious observation (obvservation?): there are no octaves anywhere, so every triad will have one note played twice in the 4-note grouping.  

Ex. 1 Triads Within a Major 7th
Ex. 1 Triads Within a Major 7th

Well, that’s a good exercise, but it is rather limited! What if we expand the range by one semitone? Now we have a full octave, C to C. That one note actually opens thing up quite a bit! Now we have an octave on the root of C major, on the 3rd of Ab major, and on the 5th of F major. Cool!  

Ex. 2 Triads Within an Octave
Ex. 2 Triads Within an Octave

What if we wanted to find the minimum range that would allow each of the 12 triads to have at least one octave? Well, on the one hand, every note is part of 3 different triads, it’s either the root, the 3rd, or the 5th. So every note we add will add 3 more triads, right? Well, not quite, because notes that are a 3rd apart will have a triad in common. 

So let’s see how this plays out. Let’s add a B below middle C. That gives us three more triads: B major, G major, and E major. That’s a total of six triads, we are half-way there! Let’s keep going down, adding Bb gives us Bb major, Gb major, and Eb major. Wow, 9 out of 12 covered! 

This time, let’s add a higher note; we’ll add C#. That gives us C# major, A major, F# major. Oops! Not quite 3 more, because F# and Gb are the same. It makes sense, because we said that notes a 3rd apart will share one triad, and Bb and C# (or Db) are a 3rd apart. 

OK, we are at 11 out of 12. Let’s add one more higher note, D. That gives us D major, Bb major (which we already had) and G major (which we already had). Woohoo, 12 out of 12. Why did D add only one new triad? Well, it is a 3rd away from Bb, so shares a triad there, and it is a 3rd away from B, so shares a triad there too!  

Now we have all 12 triads with at least one octave. By the way, you know those triads we said we ‘already had?’ F#/Gb major, Bb major, and G major? Well, those ones have two different notes with an octave.   

Ex. 3 Triads Within a Major 10th
Ex. 3 Triads Within a Major 10th

So, to summarize, the smallest interval that will allow you to cycle all 12 triads with at least one octave per triad is a major 10th

OK, this is all good so far, but the motion rule is a little bit dull. Let’s try throwing in what Barry Harris calls pivoting. Pivoting breaks up the motion of an arpeggio, or broken chord, by adding an octave displacement, either up or down, and then continuing. In this example, we will play a note, pivot down to the next chord note, and continue upward for 3 notes. We’ll then chose the closest note in the next chord and repeat the process. This way all of the 4-note groups will have a similar countour.  

Ex. 4 Triads Pivoting Within a Major 10th
Ex. 4 Triads Pivoting Within a Major 10th

That’s all for now!

The next note is never more than a whole-tone away

I first learned of the exercise of running different scales into each other from Barry Harris. You start near the top of your instrument, and as the chords change, you change your scale but keep going in the same direction. Relatively easy on a tune like Autumn Leaves, pretty difficult on a tune like Giant Steps. My teacher Mark Sherman also emphasizes this drill, and has in fact taken it to a whole new level.

In discussing this drill a few weeks ago, Mark told me, the next note is always either a semitone or a whole-tone away. I thought of a simple way to prove this.

First off, we need to review the concept of locally diatonic scales. In short, they are scale in which all groups of three consecutive notes can be mapped onto three consecutive notes of the diatonic scale. There are only four scales that qualify: diatonic, melodic minor, whole-tone, and diminished. None of these scales contains an interval greater than a whole-tone. Both the harmonic minor, and its inversion, the harmonic major, contain an augmented second, that’s why they are not included.

Ok, so moving between any of our four scales, at any transposition, the next note will always be a semitone of a whole-tone away, and here’s the proof.

  • The current note will either be a member of the next scale or not
  • If the current note is a member of the next scale, the next note will either be a semitone or a whole-tone away
  • If the current note is not a member of the next scale, then the next note has to be a semitone away, by definition
  • Therefore, the next note is always a semitone or a whole-tone away

By the way, when running locally diatonic scales into each other, the aggregate result is definitely not guaranteed to be locally diatonic. It should be easy to think of examples where running two scales together results in two consecutive semitones, which would break the rules for locally diatonic.