Nehemiah 12:45
They kept the watch of their God, and were responsible for making things clean. So did the music-makers and the gatekeepers, as David and Solomon his son ordered it.
1 Chronicles 25:1-26
David and the commanders of the army set apart for the service some of the sons of Asaph and of Heman and of Jeduthun, who were to prophesy with lyres, harps and cymbals; and the number of those who performed their service was:
1 Chronicles 23:28
The duty of the Levites was to help Aaron's descendants in the service of the Temple of Jehovah: to be in charge of the courtyards, the side rooms, the purification of all sacred things and the performance of other duties at the House of God.
2 Chronicles 23:6
Only the priests and Levites who are on duty should come into Jehovah's Temple. They may enter because they are holy. The other people should follow Jehovah's regulations.