The harmonica explains all of Western music

If you want to understand the vast cultural struggle taking place in the study of Western harmony, you could do worse than to start with the harmonica. This unassuming little instrument was designed in central Europe in the 19th century to play the popular music of that time and place: waltzes, oom-pah music, and light classical. All of this music is “diatonic,” meaning that it’s based around the major scale, the do-re-mi you learned in elementary school. It’s also the harmony that you learn if you take a typical formal music theory class.

Here are the notes you can play on a C harmonica:

The top row shows the notes you get by blowing into each hole. The harmonica is an unusual instrument in that it also makes sounds when you draw (inhale). The bottom row of notes are the ones you get by drawing on a C harmonica.

The diagram below shows the C harmonica’s notes on the chromatic circle. The outward arrows are notes you get by blowing, and the inward ones are notes you get 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 cadence. It’s also called a V-I progression, because the G7 chord is built off the fifth note in the C major scale, and the C chord is built off the first note. In Western tonal harmony, the C is called the tonic chord, meaning that it’s considered “home base.” The G7 is called the dominant chord, because it creates a powerful feeling of tension that 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 ground of C.

The V-I cadence is so important to the music of Western Europe that traditional theory courses dwell on it for months before so much as mentioning other chords. The harmonica was designed to play cadences and nothing else. If you inhale and exhale, you get V-I-V-I-V-I, over and over. Through selective blowing and drawing, you can also play the individual notes of the C major scale. That’s not a lot of tonal material to work with, but it’s enough for European folk and very basic classical music.

Sometime between 1870 and 1920, Black American musicians discovered an alternative way to play the harmonica. They realized that if you just mentally reverse the roles of the blown and drawn notes, so that G7 is “home base” rather than C, you get a completely different sound. Here are the notes in a C harmonica again, but this time centered around G:

If you think of the drawn chord as being the tonic, you find yourself in a scale called the G Mixolydian mode. It’s similar to the G major scale, but with one important difference: the seventh note of G Mixolydian is F, whereas the seventh note of the major scale is F-sharp. That seems like a small difference, but it gives the two scales very different sounds. While the major scale has a plain-vanilla, classical, old-world feeling, Mixolydian sounds more exotic, more modern, and more like blues and rock. This method of treating the drawn chord as the tonic is called “cross harp” or blues harmonica.

When you play your C harmonica in the blues style, drawing still produces a G7 chord and blowing still produces a C chord. However, now G7 is the tonic because it’s built on the first scale degree in G Mixolydian. Meanwhile, C is now the IV chord, because it’s built on the fourth scale degree in G Mixolydian. In classical music, you are not supposed to feel resolution from landing on a dominant seventh chord. In the blues, however, G7 is a perfectly stable-feeling place to land.

Blues harp departs from classical harmony in another way, too: you can’t play a cadence. The IV chord creates a similar feeling of suspense to the V chord, but it’s weaker and less tense. The IV-I progression is known in classical theory as a plagal cadence. It’s nicknamed the “Amen” progression because it appears so commonly at the end of hymns. Plagal cadences aren’t considered to have the same tension/resolution effect that a “real” cadence has.

Remember how I said that the V-I cadence is the most important harmony in all of Western classical music? Entire schools of music analysis are premised on the idea that you can reduce any piece of music down to its foundational cadences. But in blues harmonica, you can’t play “real” cadences at all. You can kind of imply the V chord with individual notes, but you can’t play the most important note, the leading tone, unless you use an advanced technique called bending.

Bending is a way of drawing on the harmonica too hard so that the notes go flat. If you bend slightly, you can get the wailing sound that the blues is famous for. Bend a little more deeply and you can play blue notes that fall between the piano keys. And if you bend extremely, you can reach new piano-key notes. (You can bend on blown notes too, but it’s harder and doesn’t sound as good.) The diagram below shows the notes you can bend on a C harp.

If you bend the G, you can get the F-sharp, the leading tone, but bending precisely is difficult, and you probably won’t hit it cleanly. When you bend B and D, you get B-flat and D-flat, the characteristic notes from the G blues scale, the basis of blues tonality. In between the major scale notes and the blues scale notes are microtonal blue notes, which are considered “out of tune” by Western European standards, but which sound perfectly correct in the blues. These may be just intonation intervals from the natural overtones of I and IV. Bent notes in cross harp also work well in all of the music that descends from the blues: rock, country, R&B, reggae, funk, and so on.

Blues harmonica shows its connection to African music in its characteristic playing styles. You don’t have a lot of different pitches to work with, so you end up doing most of your expression through rhythm and timbre, through fine microtonal shading and vocal-sounding articulation. Your chord vocabulary is limited, and you can’t change keys without switching harmonicas. However, you can get an endless variety of percussive, speech-like, and guttural sounds. It’s possible to play more European-descended music on the diatonic harmonica too, and people do, but it’s extraordinarily difficult. Playing the blues on the harmonica is relatively easy, and a lot more fun.

So here we have two worlds of music contained in a single instrument. There’s the “official” world of Western European tonal theory as taught in schools, and there’s the “unofficial” world of the blues, as taught in very few schools, but practiced everywhere in the culture, from the most abstract jazz to top forty radio. Not much music in everyday American life strictly follows the rules of Western tonality. Nursery rhymes do, because they come from the European folk tradition. Hymns, older showtunes, and very conservative pop music mostly do too, for the same reason. But most other current music is informed by the African diaspora.

Schools are very slowly beginning to acknowledge that the blues exists and that it’s worthy of study, but for the most part, the best way to learn about it is to figure it out on your own. The harmonica is an easy instrument to physically play, but a difficult one to understand. As soon as you pick it up, you’re faced with the conflict between two musical value systems. That conflict is the musical face of America’s horrific racial history. If you play harmonica as it was intended to be played, you can only produce music that sounds awkwardly old-timey. (I heard one student complain that in diatonic harmony, everything sounds like “Happy Birthday.”) If you play the harmonica “backwards,” out comes the blues, the cornerstone of America’s musical culture, and, increasingly, the world’s.

The way that blues musicians creatively misappropriated the harmonica is a neat precursor for the way that rock musicians misappropriated the guitar amp, and the way that hip-hop musicians misappropriated the turntable and sampler. Rayvon Fouché calls this black vernacular technological creativity. I can’t think of a tidier metaphor for the story of white and Black music generally.

For a more detailed explanation of how the harmonica works and how you use it, see my harmonica guide.