The harmonica as a metaphor for pop music theory

This is a reworking of an old post with clearer language and better examples

Last semester was my first time teaching aural skills in NYU’s new popular music theory sequence. This semester will be my first time teaching a full-fledged theory class in the sequence. When I have taught music theory in the past, I have always used a lot of examples from Anglo-American pop, but it’s nice to be in a program that is committed to putting that music front and center. This raises a question, though: what is “popular” music theory? Isn’t music theory just music theory? Why should NYU create a whole alternative theory sequence for pop? The short answer is that Anglo-American popular music operates by very different rules and conventions than Western European tonal music.

It’s a cliche to say that American music is a combination of European harmony and African rhythm. However, a substantial amount of Anglo-American pop harmony is African-descended. The blues has especially strong African retentions. (It’s a problem that theory curricula are so heavily weighted toward harmony and voice leading. We need to include much more rhythm, form and timbre in theory class! But that is a discussion for another post.) You can understand the difference between blues harmony and Western European harmony by looking at the evolution of blues harmonica.

The harmonica was invented in central Europe in the 19th century. More accurately, it was adapted; its free-reed construction was modeled on Asian instruments like the sheng. The most common harmonica design uses Richter tuning, which limits the instrument to a particular diatonic scale. This makes it easy to play waltzes, oom-pah, and light classical. The Richter-tuned harmonica became part of American folk tradition as well, in a style that players now call “straight harp” or “old time harmonica”. Here’s YouTube user 1seesaw2 playing “Oh My Darling Clementine“.

Unlike most other wind instruments, you can play notes on the harmonica both by blowing and drawing (inhaling) through it. Here are the notes you can play on the ten holes of a Richter-tuned harmonica in the key of C, with the blown notes on top and the drawn notes below:

The diagram below shows the C harmonica’s notes on the chromatic circle. The outward arrows are notes you produce by blowing, and the inward ones are notes you produce by drawing (inhaling). You can play G by both blowing and drawing.

Together, these seven notes form the C major scale. The blown notes (C, E, and G) form a C major chord. The drawn notes (G, B, D, F, and A) form a G9 chord, that is, a G7 chord with an additional A on top. Together, G7 and C form a chord progression called a V-I cadence. The G7 chord is built on the fifth note in the C major scale, and the C chord is built on the first note. In Western tonal harmony, C is called the tonic chord, meaning that it’s considered “home base.” The G7 is called the dominant chord. It creates a powerful feeling of tension that “dominates” the other chords, and the tension can only be resolved by returning to the tonic. The word cadence is from the Latin cadentia, “a falling,” and you can think of it as a fall from the precarious perch of G7 to the sturdy ground of C.

The V7-I cadence is extremely important to the music of Western Europe. This is why traditional tonal theory pedagogy focuses on it so intensely. The harmonica was designed to play V7-I cadences and nothing else. If you inhale and exhale, you get V7-I-V7-I-V7-I, over and over. Through selective blowing and drawing, you can also play the individual notes of the major scale. That is not a lot of tonal material to work with, but it’s enough for 19th century central European vernacular music, and the American music that derives from it.

Sometime between 1870 and 1920, Black American musicians realized that you can get a very different sound from the harmonica by mentally reversing the roles of the blown and drawn notes. If you think of the drawn notes as the tonic chord, then you can play a C harmonica in the key of G. The drawn G9 chord becomes the I chord, and the blown C chord becomes the IV chord. This playing style is called “cross harp” or “blues harp”. Here are the notes in a C harmonica again, but this time centered around G:

Here’s the great Sonny Terry playing cross harp.

Playing the C major scale from G to G produces a scale called G Mixolydian mode. It’s similar to the G major scale, but with one important difference: the seventh note of G major is F-sharp, while the seventh note of G Mixolydian is F-natural. The first, third, fifth and seventh degrees of G Mixolydian form a G7 chord. There is a tritone between the B and F in the chord, which European classical theory considers to be an inherently unstable and dissonant interval that demands resolution to a C chord. An entire school of classical music analysis is premised on the idea that you can reduce any piece of music down to dominant seventh chords resolving to tonics. In blues in G, however, G7 is not an unstable or dissonant sound.

In straight harp, all you can play are V7-I cadences. In blues harp, on the other hand, you can’t play the V7 chord at all. In G blues, you can imply it by playing A and D, but there is no F-sharp on a C harmonica. When you alternately blow and draw, you get bluesy plagal cadences, IV to I7.

Theory teachers from the Western tonal tradition will sometimes explain the I7 chord in the blues as a secondary dominant, V7/IV. In tonal theory, G7 always tonicizes a C chord, it can’t be a tonic unto itself. Sometimes the blues does use secondary dominants, but for the most part, seventh chords don’t “function” in the tonal theory sense. More accurately, they do function; they just don’t function like European V7 chords.

In addition to the flatted seventh, there are two other non-diatonic notes that are characteristic of the blues: the flat third and flat fifth. In G blues, these are B-flat and D-flat. These pitches are not available on the harmonica as it was designed, but it’s possible to play them using a technique called bending. If you hold your tongue in a certain position while you draw, you can make your notes go flat. To play blues in G, you bend B to produce B-flat, and you bend D to produce D-flat.

Blues players also need to be able to play blue notes, that is, pitches in between the equal-tempered (piano-key) notes. In the previous paragraph, I said that you can bend B down to B-flat in G blues, but in practice, blues harmonica players bend to many different pitches between B and B-flat, and sometimes between B-flat and A as well. Blues players bend D through the entire pitch zone between D and C. They also bend F toward E, and sometimes a bit past it. It’s possible to bend any drawn note, and if you work at it, you can bend the blown notes as well. However, blues players mostly bend to reach pitches in the zones below the equal-tempered third, fifth and flat seventh.

Blue notes are a profound music-theoretical mystery. Why should it sound so good to play certain notes deliberately out of tune? One hypothesis says that blue notes are not out of tune at all, they are actually more in tune than standard equal temperament. Gerhard Kubik argues that blues harmony originates in West and Central African tuning systems based on the first seven natural overtones of notes tuned a fourth apart. This might explain why, in the middle decades of the twentieth century, Hohner manufactured its harmonicas to play a just intonation tuning that produced blues-friendly intervals, including the just major third (a little flatter than the equal-tempered third) and the harmonic seventh (much flatter than the equal-tempered flat seventh). Hohner apparently thought that this tuning would be more appealing to blues players than equal temperament, and blues harmonica players apparently agreed with them.

Every beginner blues harmonica player confronts the confusing fact that the key stamped on the instrument is not the key you are supposed to play it in. Why do you need a C harmonica to play the blues in G? Why not a G harmonica? It took me many years of self-guided study to understand that the instrument embodies two conflicting systems of harmony. Playing the harmonica as it was intended to be played only produces music that sounds “white” and old-timey. (I had one student complain that in diatonic harmony, everything sounds like “Happy Birthday.”) To play the blues, you literally have to play the harmonica backwards.

Beyond its pitch content, blues harmonica shows its connection to Afrodiasporic tradition in its playing style. The instrument does not offer many different notes to work with, so players end up doing most of their expression through rhythm and timbre, through vocal-sounding articulation and shaping of dynamics and overtones and noise. The speech-like “wah wah” effect that blues players do with their hands is a case in point.

You can produce speech-like vocalisms on other instruments too, but the harmonica practically requires them, because it is so limited in other ways. You can learn the melodic and harmonic basics of blues harmonica in an hour, but getting it to talk and wail takes many years of practice.

Blues harmonica is worth understanding in its own right, but it also has broader symbolic importance for music education generally. Theory classes and teaching materials centered on Western European tradition rarely mention the blues at all. When they do, they tend to present it as a deviation from the normative rules of Western tonal theory. However, blues is a coherent musical system unto itself, and we should teach it as one. I said above that blues musicians play the harmonica “backwards”. From the perspective of the harmonica’s intended design, that word is accurate. However, in my experience as a player, blues harp is “forwards” and straight harp feels “backwards.” I would prefer that music theory class presents the blues as an alternative form of consonance, not as “dissonant” or “out of tune”.

Blues harmonica is also important as an example of what Rayvon Fouché calls Black vernacular technological creativity. Other examples include Tricky Sam Nanton and the trombone, Jimi Hendrix and the guitar, Herbie Hancock and the vocoder, Grandmaster Flash and the turntable, Pete Rock and the sampler, and T-Pain and Auto-Tune. There is a rich history of Black Americans finding innovative and unexpected uses for instruments and other music technology. I find this history to be inspiring.

I’ll end this post by returning to the question of what popular music theory classes should teach. It’s not (only) a philosophical question, it’s a practical one. As music departments open the door to more non-classical music in the theory sequence, educators have to decide what to include and what not to. I would like us to put the blues at the center of our teaching to reflect the central role it plays in the past hundred years of Anglo-American popular music. Blues harmony is a big and complex topic; studying the harmonica is an excellent jumping off point.