Xenharmonic music is any music that uses pitches outside the twelve standard notes in Western music. Much more information can be found here, but don’t get discouraged by the sheer depth of the theory.
As a trombonist and slide guitarist, I like to joke that I’ve always been playing microtonally, especially on my worst days. But honestly, when I first learned about the idea of microtones I dismissed it immediately. I had only been exposed to quarter tones and 24-tone equal temperament, and it sounded very sour. My delicate ears really couldn’t stand to give it a chance. And when you try anything new, you need to give yourself time to acclimate to music that, at first, just sounds purposely out of tune.
24-TET might seem like an obvious way to start out with microtones: just split the twelve notes in half! You can tune two pianos one quarter-tone apart to get the full scale. You can keep all twelve familiar notes, and all their well-explored relationships with each other. Plus you get a whole new circle of fifths that’s one quarter tone away from the familiar one, which also has all the same relationships you’re used to.
I don’t think 24TET is the best introduction to microtones. To explain why, we need to dig into the tuning theory a bit, which can be a fascinating rabbit hole. But it can also be an absolute minefield of jargon and abstraction. So if you want to learn more, I recommend spending lots of time listening and experimenting, in addition to any reading you can do.
Interestingly, the two circles of fifths don’t intersect at all; they’re two separate circles with no common notes between them. This hints at why I thought it was sour. If you compare the frequencies of two neighboring notes in a 12-TET circle of fifths, you’ll see the ratio is very close to the pure 3:2 interval. This sounds almost as consonant as an octave. However, in 24-TET if you compare frequencies between notes from both circles of fifths, the ratio is not nearly as simple, which means the frequencies don’t resonate as well with each other. Sidenote: There are a couple really neat exceptions; in 24-TET you can find reasonable approximations of the 11:8 and 7/4 intervals, which are really pretty and consonant, but just plain missing from 12-TET. That gives them an exotic but accessible flavor that’s really useful for a musician or composer.
So, TL;DR: like many musicians, my first exposure to alternate tuning systems left me with the assumption that microtones add a lot of complexity, but don’t offer compelling new possibilities. What changed my mind about microtones? First, I found a song called Gleam, by an artist named Sevish, which you can hear here:
It’s in 22-EDO, which is 22 equal divisions of the octave. This tuning is exotic in a lot of ways, but music makers have found fascinating ways to use its notes. Something about Gleam pulled my ears in, rather than pushing them away, and I felt a sense of fascination that needed feeding. I dug the lopsided groove and the strong bass line, and the harmonies are like distorted reimaginings of some of my favorite jazz & fusion chords.
Youtube’s algorithm then brought me to other microtonal content, including this fascinating video about the Bohlen-Pierce scale, which is wild in that it replaces the octave (ratio 2:1) with the twelfth (ratio 3:1) as the interval of equivalence. I doubt I’ll ever fall in love with this scale, but it was just so gutsy to be tossing out the idea of an octave, my curiosity got the better of me.
At this point, I’ve heard music that makes great use of 24TET (Fever by FastFastFast is a great example). There’s a disorientingly cool technique in use here where the chord progression sneaks a jump from one circle of fifths to the other. It’s subtle in that the harmonies themselves vertically are very familiar, but in the progression, the roots of two neighboring chords might be three quarters of a whole tone instead of a real whole tone.
So, the music I’ve found is what has drawn me into xenharmonics. Having heard this compelling art, I’ve now spent lots of time trying to understand the theory, and I have a grasp of some of the basics. But xenharmonics/microtonalism is really not one monolithic set of ideas. It’s a huge umbrella term, and underneath it are many different approaches. Each one has something to offer, and could easily consume one’s whole creative career. I have started to focus on becoming a practitioner; a musician and maker. I am looking for ways to get these notes into the hands of musicians. I want it to be more practical for artists (and me) to make xenharmonic music.