Making a custom brass instrument?

This actually is correct -- good guess. As I've mentioned, I'm an
absolute novice, so I'm not suprised I didn't supply enough
information; I'll try to be a bit more specific -- here is what I'm
trying to replicate or at least get something similar to:

http://devnull.dtcc.edu/gfx/brass.jpg

The body (lower part is 1/2" pipe) and the top part where it's most
wide is 3/4" -- I don't think it's a conventional brass fitting or
adapter, so I'm assuming it was either manufactured or somehow tapered
into that shape. Hopefully this is a bit more information and the
photograph will help.

Thanks for the advice and patience!

Rob