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Comment by thenoblesunfish | Hacker News Reader

The big question underlying this kind of analogy: are the spectra of visible things (EM) and the spectra of mechanically vibrating things similar? Naively, I'd say no, so this is yet another fun but ultimately arbitrary mapping which people endlessly invent to make music. Is it deeper than I think at first glance?

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Check out this page https://chromatone.center/theory/interplay/spectrum/ - there's this exact question answered with diagrams and an interactive tool down in the bottom of the page. It shows that just by going up in octaves you get to THz territory on the 44th octave step and the frequency of note A44 matches red color. And other notes fall on the spectrum quite spectacularly.

I get it why this analogy is so tempting. If we consider the visible wavelengths being from 380nm to 780nm, that’s almost precisely one octave. If we could see the “ultraviolet octave”, and/or the “infrared octave”, would it resemble a rainbow? Would be neat if it did. When I was a kid, I wondered if violet and red were actually the same color, somehow. To me personally it feels like red and violet have much more in common than blue and green, for instance.

Physically, they're pretty analogous. But perceptually, sound and sight are very different. We're much less interested in abstract visual arrangements and there's no visual analog of harmony.

Maybe I'll add that our "detectors" for sight and sound operate on different principles.

Our sight system is a camera, capturing a 2-D image of the world. Color is picked up by 3ish sensors that have broadband frequency responses, meaning that a huge amount of information on the actual spectral content of the light is discarded. Countless spectral combinations get flattened into individual color values.

Our sound system approximates a Fourier-like decomposition of sound into frequency bins at points in time. It preserves much more spectral fidelity, but very little spatial fidelity.

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