These are the leaders of the singing men, according to the families of the Levites, who were dwelling in the chambers, so that they might carry out their ministry continually, day and night
Other versions
King James Version
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. English Standard Version
Now these, the singers, the heads of fathers' houses of the Levites, were in the chambers of the temple free from other service, for they were on duty day and night.New International Version
Those who were musicians, heads of Levite families, stayed in the rooms of the temple and were exempt from other duties because they were responsible for the work day and night.