Nickel silver is currently my favorite metal. REAL mellow sounding, almost gold-like. Gives you a real intimate sound (and who doesn't love getting all sexied-up with your trumpet at times?
). Works good with lacquer, as I found lacquer wont kill the tone with nickel silver.
Red brass also gives you a warmer sound, but its nowhere near as noticeable as I like. I imagine gold plating over red brass would make some difference.
Copper is the darkest of the dark. I'm not really well-acquainted with copper, so I'll step down and give someone else the podium on this topic.
Yellow brass gives players better control, but doesnt make for a darker sound. Kind of a middle of the road. Again, I'm not VERY knowledgeable on yellow brass (Though I SHOULD)...
Sterling silver, good gravy, sterling silver. If you are a naturally bright player, for the sake of your audience's ears, stay away from this...
Then there was beryllium. Not something for a chamber group. I would love to hear from someone who played a beryllium bell horn.
PLATING
Gold is the warmest, and most expensive of the platings. If you plate gold, plate 24k, for the best effect. 14K is mostly copper, and your killing the point of even getting gold then.
Silver is known for brightening the sound. I think silver looks best when paired with gold, personally.
Lacquer is kinda the weird one. Some people love it, some hate it. Some thinks it darkens, and makes the sound fuller. Others think it kills the sound. Try a few lacquer horns before you buy.
Nickel is a weird one, not normally found on trumpets. It gives the sound a much ringier tone, and brightens as well. Another thing, is I've found nickel reacts to my hands much quicker than other platings. I will say thats a weird thing with me, nickel is supposed to be better about not reacting than the other platings!!
COPPER plating? Yes, it exists. I don't know ANYTHING about it, though.
Double Silver plating? Yes, it exists. Darkens the sound considerably, and adds weight to the sound, though it will still have a silverish ring to it.
Shotblast lacquer? New one on me. Glass in lacquer? Sounds dangerous, really (Pictures shards of broken glass sticking out of a horn). In all seriousness, though. The shotblast is really neat looking, giving the horn an almost icy look. Its supposed to give weight to the sound, but with the glass particles, give the horn a unique ring of its own.
I think I've covered most of the bases.
Van