Re: how does the material of the saxophone affect the sound?
It does slightly change the sound and response, but don't expect dramatic results from the plating or material on its own. Most of it comes from how the sax is made.
Its generally accepted that:
Bare Brass feels more resonant and "alive."
Lacquer of any color is a little less resonant because the lacquer dampens some of the overtones.
Silver plating is a little brighter but sounds a little sweeter.
Nickel and Black Nickel is more punchy and brighter.
Gold plating is deeper and warmer.
and Bronze is warmer.
But the bottom line is the sax not the finish. No two saxes are identical so a silver plated Mark VI might be significantly darker than a Lacquered Mark VI.