I've been through this process. No amount of mouthpiece will make a euphonium sound like a baritone. I learned this when playing in a brass quintet. Sometimes, the piece will "call" for a mellow rich sound and the euphonium fits nicely with the horn, tuba, and trumpets. Sometimes, you really need a trombone. Same is true with baritone. The euph is just full and rich, even when played on a small mouthpiece (as in a 6 1/2AL with a medium to tenor adapter in your 2900). It will still sound like a euph. The sound will be "big" and fill the space, even if it is just a bit thinner than with the 4AM, 51D, or BB1.
I find this true as I switch between baritone and euphonium. I play a 4AL on euph and a Bach 5G on baritone. I also have a Bach 5G (large shank) for doing warmup and daily routine on the euphonium on days when I will be playing baritone. I sound VERY different on the two instruments, even when using using similar mouthpieces.
Doug
PS. I got rid of my Holton Superbone because I found I COULD make the baritone sound like a trombone (almost). When I need to play both euph and trombone parts, I hide my baritone under the chair and switrch instruments when necessary.
Adams E3 0.60 Sterling bell - Prototype top sprung valves
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