military bandsman
Refers to a musician serving in a military band. A somewhat specialized term; in modern contexts, 軍楽隊員 may also be used.
He enlisted as a military bandsman when he was young.
Compound of 軍 (gun, 'military') + 楽 (gaku, 'music') + 手 (shu, 'person'). The exact historical derivation is uncertain, but the term follows a common pattern for occupational nouns.