Just the plain steel unwound strings, one brand to another, no coatings, no cryogenics. Same gauges, comparing apples to apples as much as possible. It doesnt seem like there would be a noticeable variance in plain old music wire but to me there are differences as often as not. Differences in sustain, stiffness, tone. If its not my imagination or my biases, then what are the dynamics and the metallurgy involved?