I was just listening to a song with a snare played with brushes, which is like white noise. Nothing mystically happend to the sound of the other instruments or vocals
I suggest bushes are not that much like white noise. Broad band yes, but all the timber of the skin, snare springs, impacts, slide, or if on the cymbals. White noise is full spectrum, equal energy at all frequencies. I think we recognize brushes as intentional, so maybe our brain processes it differently from true noise. But I agree, they do not change the timber of the other instruments. Now, what is the difference if masked by bringing the noise floor from -120 to -90? Would that mask all the harmonic distortion? Or does our ability to distinguish sounds below noise come to play. How much?
The more I think about it, the big audible difference I experience is at a much higher level. With the D30 or Asgard, I had to drop 3100Hz by 4 or 5 dB and roll off 6000 to 20000 by 5 for it to be comfortable. My room is pretty bright and my speakers are too flat. With the ATOM, I only come down 1 to 2 dB and roll off 3 depending on the recording. Whatever the "bad" sound is, it is a trigger, on-off. There or not. So it is a threshold my brain senses. More confusing, it is seems to sense it relative to the level up to a point. Turning volume down 3 dB from "comfortable" listening did not make the glare go away. More does. Louder made it worse, but was still on-off with respect to the other frequencies. Of course, the difference in EQ also brings up details on some recordings when they are there, but that is not the difference I am referring to. That is simple EQ differences anyone can hear and measure.
The objectionable sound does seem related to sounds with a lot of higher frequency content. Cymbals, or female vocals with lots of overtones. Joni Mitchel can really nail the glare, where Amanda Mcbroom does not reach it. A trumpet can, but a flugelhorn does not. Woodwinds don't seem to. I can only explain what I hear to see if spurs on a thought on the cause and possible measure.
Maybe another question is what combination of sounds, original or created, fool our brains into thinking what we hear is real? Are their other clues related to timing and phase our brain is processing. A harmonic delayed or out of phase? Harmonic balances not what we expect from nature? More or less high order? Balance even to odd?
I wonder if our digital analysis can determine phase relationship with the harmonics. If so, recorded sounds would be such a mess already it would not matter logically. Maybe something though as the only almost real I ever heard was 2 mics to a Revox, and played back directly. No mixing or production, no Dolby, no additional eq, nothing. I don't remember any tape noise. Old B&W 801s have been surpassed, but it was darn convincing. I would expect the total end to end distortion was very low, even if the equipment of the time did not match up to the best today. (Levenson amps, so no slouch either)
Let's think. Someone out there may have the epiphany we are all waiting for