You can play with an online synthesizer to create timbres whose octaves are dissonant:

https://raw.githack.com/CindyJS/ScaleLab/master/index.html

There's the book by Dave Benson [0] (available online), mostly about the mathematical modeling of instruments, that has a nice ethnomusicological compendium of instruments with weird timbres.

And then there's the infamous book by Sethares [1] that is all about the dependency of harmony on timbre.

[0] https://homepages.abdn.ac.uk/d.j.benson/pages/html/maths-mus...

[1] https://sethares.engr.wisc.edu/ttss.html

1:2 is special in that it gives the maximum possible consonance when using harmonic timbres, but there are other good scales built around different ratios. See:

https://en.wikipedia.org/wiki/Bohlen%E2%80%93Pierce_scale

https://en.wikipedia.org/wiki/Gamma_scale

You might want to be wary of your bias. From your statements, it seems as though you're somewhat dismissive of this study and are searching for studies/sources that support your point of view. If you find yourself dismissing the person you're replying to and other comments in this thread, even though they raise interesting points about instruments, you might want to think about whether you're being open-minded.

Maybe. If you knew me, I think you'd be hard pressed to label me as someone who isn't open minded. But these are not arbitrary positions. I study harmony intensely, integrating neuroscience, music theory and classical philosophy. Did you know that the Pythagorean test of small integer relationships in consonant bronze chimes (described by Plato and Aristoxenus) is considered to be the very first quantitative, hypothesis-driven experiment in western history? And yet, we still don't know the basis for consonance and dissonance!

I will only say that my "bias" got me what I wanted-- evidence about the phenomena! (And thank you for that)

I think that the OP is maybe making too much drama about it. Skepticism (even extreme skepticism) is always welcome in a scientific/technical discussion!

EDIT: Regarding the basis for consonance/dissonance, the mathematical part of it is straightforward. When superposing pure waves of close frequencies you obtain beating (a slow frequency modulation of the amplitude of your sound), and beating does not appear when you superpose pure waves of very different frequencies, regardless of the interval, integer or not. Thus, the only dissonant intervals of pure sinusoidal waves are those that are very close to the unison. If you compound this with the fact that western instruments have harmonic spectra, you see why some intervals are consonant and dissonant: the dissonant intervals are those that have some partials that are close, but not exactly, unison.