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Take off the slide of a trombone, put a mouthpeice into the hole where the slide goes. TAADADADAA!!!!!!!!!

Resembles a euphonium/alto horn when bell points backwards
Trombonist: I was so bored at band camp i played tromphonium

All other band members: (shiftty eys) Yes, indeed...????~~!!!

Drummers: huh?
by Hsdfdfghfadfdf April 21, 2007
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