The character first appeared in the short story "Sing a Song of Mallworld," published in the Spring-Summer 1980 issue of Isaac Asimov's Science Fiction Magazine (vol 4, no. 7).
I was still in the showoff stage then. I guess everyone goes through it, but in hindsight it gives me little shivers of embarrassment. You have this huge, four-layered twelve-octave keyboard, each tone adjustable to the 66 subdivisions of the octave, with selectable overtones. You have this gigantic chromatic apparatus that sends out spurts of color and spins exquisite patterns in the air, and you can key the colors any way you want. You can have each tone correspond to a point in the visible light spectrum-that’s the standard setting- or any other settings; you can generate random correspondences or have correspondences in any pattern you want, simple, quadratic, whatever. The keys are so sensitive that the slightest pressure change in your fingers can alter the whole perspective. You can subvoke instructions to a hundred little black boxes for new patterns and images. And with the psifi, you’d add a whole ’nother layer of meaning and texture to the piece....
I couldn’t resist trying out Dad’s present, even though I’d never practiced with a psionically sensitive instrument in my life. But I was just a kid.
I hung on until the hush was complete. Annetta hung from the pointed ceiling, completely outside everything.
Then I launched into Light on the Sound.
That’s one of the most famous pieces ever written, and I couldn’t really play it. I started it too fast and decided to bluff the thing out. I sent out volleys of starclusters to counterpoint the dizzy fournote lefthand ostinato, then improvised some patches of glitterwhorls over a deep blue background that I sustained with the foot pedals. In the background I could hear them gasp- the gullible philistines! Anyone can do fireworks on a clavichrome.
"Light on the Sound,” is an actual real musical piece composed by Somtow for piano virtuoso Violet Lam.
The instrument is also mentioned in passing in the 2012 sci-fi novel Farthest Reef by Karl Kofoed.