Building Up From Three
Lately I’ve been focusing on triads: three core notes of a scale, built on the primary dyad of root and fifth (1–5). Since in one direction (ascending) that interval is a fifth, in the other direction (5–1) the interval is a fourth. Likewise, 1–4 is a fourth but 4–1, going up to the next octave, is a fifth.
It’s easy to identify these core notes starting from the root:
1
1–5
1–4–5
What’s more intriguing is to realize that this identical structure of intervals can carry different modal numbers as part of six primary scale variations. The core triad C–F–G is common to each.
It’s easy to see why a large portion of rock, blues, and jazz progressions rely on the same 1–4–5 and 1–2–5 structure, since this triad gives common notes to play across neighboring scales within a song arrangement. It’s more versatile than the common major or minor chord structure of 1–3–5, which rather serves to distinguish the unique signature of its key, with direct linkage only to the two closest neighbors:
So let’s call our 1–4–5 structure a modal trial, as distinguished from the 1–3–5 chordal triad.
Another advantage for improvisation is that the transpositions of the modal triad gives us five variations to try on the standard and alternative pentatonic scales (of which the best known mode is 3, the In Sen scale in G, below).
Note that the 6–2–3 sequence bridges the two different pentatonic scales, containing the common essence of both C Minor pentatonic, and C In Sen.
Turning to the physical flute, the layout and fingering support the same structure even as the scale progression ascends through the circle of fifths. In the chart below, each row shows the modal triad common to all five scales in the range indicated, from the Circle of Fifths.
Having established the essential triad in modal play, the next step is to find the best fourth note to add. So far we are using intervals of fifth, fourth, and second. The 1–2 in fact mirrors the 4–5.
So intuition, and a glance at the above chart, tells us we should apply the same close link to the lonely note left out. In the case of C–F–G, the C needs a hand-in-hand companion, either the D or the Bb. Remarkably, regardless of which companion we choose, the same interval structure applies across the scale.
Whereas each modal triad is found in a range of five neighboring scales in the Circle of Fifths, each variant with a fourth note added (1–2–4–5, or transposed as 2–3–5–6 or 5–6–1–2) is found in a range of only three neighboring scales. The complete progression through all keys is shown in the chart below.
To add a fifth note and arrive at the pentatonic scale, we have reached a closer correspondence with the diatonic major scale. The additional note added to 1-2–4–5 is the 3, filling out the standard pentatonic scale as 1–2–3–5–6. Only one other transposition applies: 4–5–6–1–2.
Which brings us back to the primary dyad, 1–5, or 4–1. We can play the above sequence of five notes with both C and G Major and it will sound good. The difference is that resolving on the C (1) gives us a major feel, while resolving on the G (5) lends a slightly different feel of the dominant. Starting with G and playing 1–2–4–5–6 isn’t really a new pentatonic scale, it’s just a mode (5) of the standard pentatonic scale starting at C (1–2–3–5–6).
So to complete our previous chart of four-note sequences, we simply add the 3 in the appropriate spot, yielding the central scale of the previous range (bold).
Again, the 3 note references the distinctive major chord (1–3–5) of a given key.
Summary:
To play in the narrow range of a single scale or its corresponding fifth (e.g., C–G), use the chordal triad (1–3–5) or the standard pentatonic scale (1–2–3–5–6).
To expand the range of progression to three or five related scales, pare the choices to four (1–2–4–5) or three (1–4–5) notes, respectively.