A “constant structure” is a fixed set of relationships between pitches. It is related to the ideas of a “pitch cell” that can be transposed and/or sequenced.
Constant structures are great for creating motivic units that add a sense of unity to your solos. I sometimes also refer to constant structures as “melodic shapes” or “motivic cells.”
To set up and use a constant structure, you’ll play a phrase (or even an entire chorus or complete solo) using one set of interval relationships that you move around via sequencing and transposition. It’s essentially a very focused way of creating motivic development.
Your constant structure could be as simple as two or three notes or as complex as a 12-tone row.
One common example is the use of major triads as a unifying principle to tie together melodic statements while improvising. For example, check out my discussion of improvising exclusively using triad pairs on “Stella by Starlight.” Another common example is the use of minor or major pentatonic scales.
Likewise, I use the constant structure approach in my discussion of “Giant Steps” — the constant structures in that post include using triads, seventh chords, and 1-2-3-5 diatonic patterns.
I want to take the concept of constant structures and expand it beyond triads, chords, and other common and familiar melodic shapes.
In a sense, anytime you improvise using a few diatonic scales in a row, you’re already using a constant structure since the underlying pitch content is the same — a major scale or one of its modes — just transposed from one key to the next.
For example, again see the part of my discussion of “Stella by Starlight” where I try to use the melodic minor scale over as many chords as possible, transposing it when appropriate.
The constant structure in this case — the unifying conceptual and melodic element — is the melodic minor scale and the interval relationships of that scale.
The melodic shape you use as your “master shape” — or guiding set of interval relationships — can be whatever you imagine! Constant structures work best if they convey good voice-leading, however.
Below are some examples of melodies built using constant structures over a II-V-I in C major.
Use these introductory examples as an inspiration to start coming up with your own melodic/harmonic shapes and practice slowly transposing them through chord changes in a way that voice leads clearly, then add varied rhythms to turn your shell ideas into full-blown melodic statements.
Keep in mind that constant structures don’t have to be three notes, they can use as many or as few notes as you like. I just happened to pick a few three-note cells for the examples here.
Feel free to also visit my website for more free tutorials and essays about topics related to jazz improvisation.
Hope you enjoy working on this concept and let me know in the comments how it goes for you!