1 Chronicles 9:33
And these are the singers, chief of the fathers of the Levites, who remaining in the chambers were free: for they were employed in that work day and night. And these are the singers, chief of the fathers of the Levites, who remaining in the chambers were free: for they were employed in that work day and night.
The singers were the chief heads of the fathers' houses among the Levites. They remained abiding in the chambers of the temple. They were employed in the work of singing continually, day and night. Because of that constant employment they were free, released from other duties. Their work was service done unto the Lord just as truly as keeping the temple gates, since the night watch and the morning music were both needed, so that doing the duty the Lord assigns is service.