Answer: sousaphone

AnswerCrossword Clue
SOUSAPHONE

March king's namesake, in a way

SOUSAPHONE

Marching-band instrument

SOUSAPHONE

Big brass

SOUSAPHONE
Large tuba
SOUSAPHONE
Instrument
SOUSAPHONEBand member's instrument
SOUSAPHONERelative of a helicon
SOUSAPHONEBrass wind instrument