or bass trumpet...
There is a nice little article in this quarter's ITG Journal called "Sliding My Way to Success" by Rob Walker. It is discussing the idea that practicing on bass trumpet or valve trombone or slide trombone (I'd add euphonium) can actually help you with your chops.
I made honorable mention in the article. When Rob contacted me with some questions I had no idea I'd be mentioned in the article.
Seriously, it's a terrific piece. Check it out.
Page 66 of the June 2009 ITG Journal.