submaster
/ˈsʌbˌmɑːstə/ /ˈsʌbˌmastə/noun
1A deputy master; a subordinate or assistant master in a school, etc.; an assistant headmaster.
2A copy of a master of a sound recording, film, etc., from which further copies can be made.
Origin
Late Middle English. From sub- + master. Compare post-classical Latin submagister, French soubs-maistre, soub-maistre, soumaitre.