Sounds like the guy at music and arts may have gotten the Finish and Material discussions mixed up a bit.
With finish, you've got pretty much silver and/or gold plating, and some type of lacquer. Of course there's also raw brass, which has no finish on the instrument.
With material, The ones you usually see are Copper alloys with Zinc in them, or Brass. Yellow brass is 70% Copper and 30% Zinc. Red brass is 90% Copper and 10% Zinc. In between those are alloy referred to as Gold or Rose brass, but there is some dispute over the composition. Usually 85% copper and 15% Zinc is rose/gold brass, but some mention 80/20.
There is also Nickel Silver, also called German Silver, which is Copper, Zinc, and Nickel, usually int a 60/20/20 ratio. It is usually used for fittings and outer tuning slides on many instruments, but my Sterling Euphonium has a body made entirely out of Nickel Silver, while the bell is Red brass I think. It's all silver plated so I can't really tell on the bell.
Sterling Silver can also be used, as can pure Copper, but those are fairly rare. Also certain bronzes can be used. The LEGENDARY Trombone tech/builder in the Los Angeles area, Larry Minick, made some one off bass trombones with Beryllium Bronze bells, which today are highly sought after.
As an Aside, the name that the actual foundries who make brass use are quite different than what the brass instrument industry uses. For them, 70/30 is "Cartridge Brass", 80/20 is "gold Brass" 85/15 is "red brass" and 90/10 is "Commercial Bronze", even though without tin, it's not a real bronze.
Last edited by tbonesullivan; 12-07-2019 at 06:12 PM.
Sterling / Perantucci 1065HGS Euphonium, 1952 B&H Imperial Eb Tuba, and a bunch of trombones.