What if the Bach Chaconne was modal jazz?

As I struggle my way through the Bach Chaconne on guitar, I’m having to work around the fact that I am great at music theory but terrible at note reading. So before I could play the piece, I had to completely understand it and be able to feel it by ear. The only way I could make the score useful to me was to go through the entire thing and write in jazz-style chord symbols. I know that this approach is “wrong,” because Bach didn’t think about chords as independently existing entities in this way, but it has still helped me get the piece under my fingers. Another “incorrect” but practically useful way for me to think about the piece is as a collection of scales and modes.

The scales approach can not explain everything that happens in the Chaconne. There are a few places (marked pink in the video) where the harmony emerges out of chromatic voice-leading that can’t be meaningfully described in terms of scales. Still, those moments are infrequent, and otherwise the scales approach has been very helpful.

Quick note about structure: the Bach Chaconne contains 64 phrases, each of which is four bars long, and each of which is modeled on the theme in the first four bars. You could think of all the phrases that follow as variations on that theme. For simplicity, I refer to each four-bar phrase as a “variation” whether it contains the theme or not.

There are four types of scales used throughout the Chaconne: the major scale and three minor scales. Rather than list them in the order they appear, I’ll go through them in a more conceptually friendly way. Click each scale image to play it on the aQWERTYon.

Here is D major, which is the main scale used in variations 34-52.

Here’s the F major scale, which you hear in variations 5, 6, 9, 13-19, 33, and 56-61:

Notice that’s the same collection of intervals as D major, but the note names are rotated three slots counterclockwise.

If you now rotate the F major scale three steps clockwise, moving both the note names and the intervals, you get the D natural minor scale. You could also generate this scale by taking D major and flatting the third, sixth and seventh degrees (turning the green notes blue):

Since F major and D natural minor share the same seven notes, they are close functional relatives of each other. In variations 13-18, 53, and 61, Bach exploits the ambiguity between these two scales to move seamlessly from the key of D minor to the key of F major.

The first and last scale you hear in the Chaconne is a variant on D natural minor called D harmonic minor:

You can generate D harmonic minor by taking D natural minor and raising its seventh degree from C to C-sharp. In Western tonal theory, C-sharp is called the leading tone because it leads into the tonic D. The idea is that the C-sharp is a dissonance, a tension that you want to have resolved, and D is a consonance that relieves the tension.

The presence of the leading tone in D harmonic minor also makes it possible to generate a very important chord, A7, the V7 chord in the key of D minor. To make chords from a scale, just pick a note and then go clockwise around the scale, adding every alternating scale tone on top. If you start on A and go around D harmonic minor this way, you get A, C-sharp, E, and G. Those four notes make an A7 chord, the V7 chord in D minor. If you keep going around, then you also get B-flat. In jazz terms, that gives you an A7b9 chord. If you leave the A off the bottom, you get C-sharp, E, G and B-flat, otherwise known as C#dim7. In jazz thinking, A7b9 and C#dim7 are interchangeable. If the note C-sharp makes you “want” to hear D, then the A7 and C#dim7 chords make you “want” to hear the Dm chord.

There’s one more important seven-note collection in the Chaconne, another minor variant, D melodic minor.

This is like D harmonic minor, except with the sixth raised from B-flat to B. You can also think of D melodic minor as D natural minor with a raised sixth and a raised seventh, or as D major with a flattened third. Baroque musicians liked the chords you get from harmonic minor, but in melodies, they thought the jump between B-flat and C-sharp was awkward. Raising the B-flat to B natural solves that problem. However, the resulting scale is a weird one! Most seven-note scales in Western music contain one tritone, which is their main source of dissonance. Melodic minor contains two tritones. Furthermore, the top half of the scale sounds completely major, which puts it at odds with the minor-sounding bottom half.

Here’s the derivation of the above scales in handy flowchart form:

Bach did not think of these three minor scales as being discrete entities. There was just minor, and you could move the sixth and seventh up and down as you saw fit, depending on the context. It’s interesting, then, that there’s one permutation of the sixth and seventh that Bach never uses once in the entire 256 measures of the Chaconne: raised sixth and flat seventh, which gives you D Dorian mode. Bach knew Dorian mode very well, but as far as I’m aware, he scrupulously avoided using it. I assume this is because it would have sounded antiquated to him.

So, to sum up, the Chaconne is (mainly) built from four scales: major, natural minor, harmonic minor, and melodic minor. You mostly hear those scales in D, but Bach also transposes them to other roots as well. Here’s a flowchart of all the scales in the piece, with arrows showing which ones lead into each other.

Guitarists! Find fingerings for all these scales using the wonderful Guitar Dashboard.

Apparently I am not alone in thinking about Bach’s music in terms of scales. Marianne Ploger does too, using a concept she calls “heptachord shifts.” The idea is that at any given time in a Bach piece, the melodies and harmonies are being generated by one of three possible seven-note scales ( heptachords): major, harmonic minor, or melodic minor. Ploger doesn’t count natural minor as a separate scale from major, because it’s the same collection of intervals. She has a whole formal rule set for how one heptachord can transform into another. It’s a pretty intriguing idea! But it also seems unnecessarily reductive. Like, I don’t really think that D minor and F major are the same thing at all. The center-ness of the tonic makes a difference.

Anyway, thinking of the scales is very useful, because you’re like, oh, this is just D melodic minor, I know what that is because I’ve already practiced it a bunch. Recommended.