So I've spent several days in Just Intonation world and I'm lovin it. (See my previous.)
It occurred to me that all “Western” sounds have been geared to the equal-temperament pianoforte since its invention in the Romantic period. It always used to bug me when I did violin exams that the examiner was usually a pianist, and thus habituated to equal temperament. The violin has no frets, so intuitively you're going to play intervals in something like just intonation, because it feels right. So I often got bad marks for playing “flat,” which is what a just intonation third sounds like to an equal-temperament ear.
Equal temperament makes available a brownish, beige version of all the keys, and it makes the keys roughly resonant with one another. This means you can create lots of different narratives, through modulation (key changes). This helps Romantic (and post-Romantic) music because you can tell a story with lots of twists and turns, climaxes and anticlimaxes, and yet always be sure you're navigating around a fairly consistent brown world. All neuroses have something in common I guess.
With just intonation you can't do narrative, because the keys are radically different—there's no brown world anymore, no general background against which the sounds make sense. So you're stuck with pure beginning—which I call aperture—the feeling of “is this the beginning?” or “have we started yet?” Aperture, openness.
(BTW it's fascinating to me, from the ecological criticism point of view, that narratives depend upon a consistent world. Think of The Lord of the Rings. That mysterious yet complete world, totally realized, like the Wagnerian “total work of art,” with its languages and histories and depths built in. It's the perfect product of Romantic nationalism. There's a bit of a discussion of it in the second chapter of Ecology without Nature. Bilbo Baggins sings “The road goes ever on and on.” There's this Romantic sense that at the edge of your front door, there's a road, and the road could lead anywhere into who knows what. But with just intonation there's no road. Just the front door.)
Listening to just intonation music is like looking at a very luminous, transparent color. We painted our house light purple a couple of years ago and got into a lot of trouble with the white and gray crew—the colors our painter called “death box colors.” Because all the wave forms are related to each other in rational number ways, you can kind of “see” far up and down them, and the notes slide over each other.
Equal temperament, by contrast, is about friction, because the wave forms are slightly off all the time. There's a good website on this by Kyle Gann that compares equal temperament to other products of capitalist consumerism like fizzy drinks. They're stimulating and have a kind of buzz—literally equal temperament chords buzz (try it). Fizzing brownness, like Coca Cola. Versus pellucid magenta. Stimulation and speed versus contemplative inwardness. Story lines versus stillness. Ego versus non-ego.
If you think about it, the dominance of the piano is about literally hard-wiring a certain way of listening to sound into the instrument itself, and so into all the other instruments around it. I've thought that the piano is the ultimate modern instrument, because with pianos you can hear the space inside them (thanks to the sustain pedal): piano music seems intrinsically about inner space. And yet and at the same time, this inner space is reified into this fuzzy brown. You can sort of see how the piano becomes a symbol for the commodity fetish—an object that appears to have its value directly inscribed into it. All those pre-programmed keys, ready to play anything you want, as long as it's brown. “Where do you want to go today?” (old Microsoft ad). The piano is the ultimate living-room possession. You could think of it as a sort of giant wooden cyst, like the shell of a sea creature. The metastasized cancer of the bourgeois ego.
So the minimalists started messing with this object, detuning it from the inside, to open up non-reified spaces within.
You could argue that just intonation music is perfect for our age of ecological emergency. Because in just intonation, there's no world. In our age, we're finding out that there is no world as such—once you become conscious of the environment, it stops being the brownish-beige background to all your narratives of success and failure, all your adventures in capitalism.