1 Chronicles 25:2
Of the sons of Asaph; Zaccur, and Joseph, and Nethaniah, and Asarelah, the sons of Asaph under the hands of Asaph, which prophesied according to the order of the king. Of the sons of Asaph; Zaccur, and Joseph, and Nethaniah, and Asarelah, the sons of Asaph under the hands of Asaph, which prophesied according to the order of the king.
David's government of Israel followed the plan of carefully assigning special duties to the men best fitted for them, of which the listing of Asaph's sons under his direction is an illustration. That organization was brought to perfection for every division of the priests and Levites, as well as for the civil officers and the army, when Solomon was placed upon the throne. Under this completed arrangement the four thousand who praised the Lord with instruments were divided into twenty-four courses. Each course was placed under the leadership of twelve men who were especially instructed and skillful in the use of musical instruments.