And of course you've performed chemical analysis of the copper and
insulation used in various brands of cable and found significant
differences. Sure you have.

One doesn't need to do a chemical analysis to notice that wire is available
in many different configurations: stranded, tinned, solid, copper, silver,
etc.. Same with insulation materials, which can range from rubber to teflon.
Different configurations will yield different electrical characteristics
which are easily measured, such as resistance, capacitance, and inductance.
Whether or not you can hear the differences is another story.

I suppose it doesn't matter much what wiring you use if you're playing mp3s
through Radio Shack electronics hooked up to Bose speakers.