I Chronicles 25:1, 6-7

Moreover David and the captains of the army separated for the service some of the sons of Asaph, of Heman, and of Jeduthun, who should prophesy with harps, stringed instruments, and cymbals. And the number of the skilled men performing their service was

All these were under the direction of their father for the music in the house of the LORD, with cymbals, stringed instruments, and harps, for the service of the house of God. Asaph, Jeduthun, and Heman were under the authority of the king. So the number of them, with their brethren who were instructed in the songs of the LORD, all who were skillful, was two hundred and eighty-eight.