Dyachok is a colloquial name for a category of church worker in Ukrainian and Russian history. The official name wasRussian:псаломщик, literally "psalm person". They were laymen, not included in the official hierarchy of church offices. Their duties included giving readings and leading the congregation in song during mass. Their other duties include that ofclerk in the church.[1]
"Псаломщик" .Brockhaus and Efron Encyclopedic Dictionary (in Russian). 1906.