I Chron. 25:1-26:19
After assigning the duties of the priests, David turned his attention to appointing men to be in charge of worshipping God in music. Asaph, Heman and Jeduthun had a total of twenty-four sons who were leaders of twenty-four worship groups. Each group consisted of its leader and eleven other men who were responsible for the time of their services by lot.
God made special emphasis to ensure that various individuals were responsible for playing a variety of musical instruments in worship to him. [Note that under the Christian dispensation in which we now serve, the instructions for music involve “singing and making melody in your heart to the Lord,” (Eph. 5:19). The use of mechanical instruments was omitted from Christian worship. If God had desired instruments, He would surely have given specific instructions for them as He did during the time of David.]
David assigned a special group of gatekeepers to be responsible for the security of the temple. They were identified as of the Korahites and were placed at the East Gate, North Gate, South Gate and West/Shallecheth Gate.