Before the advent of radio, public-address systems, etc, the Artillery like other mounted arms of the service, was accustomed to rely on trumpet calls in action, and it was the duty of the Trumpeter to stay with his BC at all times. Thus he was an important person in the Battery.
He carried the bugle at his right side as well as a trumpet under his left arm. Both were necessary, the bugle for sounding calls common to dismounted arms and Infantry, the trumpet for calls peculiar to the mounted.
When the Battery was in barracks the duty trumpeter was also responsible for sounding routine calls for parade, mess, etc. These were necessary for in the so-called 'good old days' few Gunners could afford watches.
Boys could enlist as Trumpeters in the RNZA from the age of 14 to 15 years up to the end of World War 1. As they grew up they became Gunners.
Between the World Wars there usually could be found among serving soldiers a few who had learned to play the instruments, and whose talents were not wasted. Calls such as Reveille, Retreat, and Tattoo sounded by a good Trumpeter were always impressive, and a pleasure to listen to. (You will never hear Reveille today; the call put across under this title is usually the Infantry 'Rouse'. Even Bandsmen avoid Reveille - it is too hard to play.)