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I tried it on F once. The recording convinced me not to do it again, the balance is impossible. Dahl definitely scored for the sound two trombones.

Got any trombone chops? Or better yet, tell them to play something else. Surely, your trumpets have wimped out on something before ("nah, man, I just don't wanna play that").

The second bone part in the Dahl is used to give some edge to the bottom voice. Often it doubles the tuba, or plays more pointed licks when the tuba lays out.

I don't think euphonium would be a good choice in this case. The goal here is to match the bite, shortness, and zip of the tenor trombone and upper brass instruments.

Perhaps a BARITONE would work

Seriously, why not just rebuild another bass bone, practice, then sell it at a profit.