In any Vedic sacrifice, four principal priests are involved. The udgātṛ is the third priest representing the Sāmaveda. His main duty is to chant the sāmans (mantras of the Sāmaveda) at the appropriate stages in the sacrifice. Sometimes he is also to perform some minor rites.
He has three assistants. They are: prastotṛ, pratihartṛ and subrahmaṇya.