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"Officers' Call" is a bugle call which signals all 
bands.army.mil
Bugle calls {{music-instrument-stub
officers
An officer is a person who has a position of authority in a hierarchical organization. The term derives from Old French ''oficier'' "officer, official" (early 14c., Modern French ''officier''), from Medieval Latin ''officiarius'' "an officer," fro ...
to assemble at a designated place.
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References
bands.army.mil
Bugle calls {{music-instrument-stub