1 Chronicles 23:5

That chant to the sound of the viol, and invent to themselves instruments of musick, like David;

As well the singers as the players on instruments shall be there: all my springs are in thee.

And he appointed, according to the order of David his father, the courses of the priests to their service, and the Levites to their charges, to praise and minister before the priests, as the duty of every day required: the porters also by their courses at every gate: for so had David the man of God commanded.

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.

So the priests, and the Levites, and the porters, and the singers, and some of the people, and the Nethinims, and all Israel, dwelt in their cities; and when the seventh month came, the children of Israel were in their cities.

And Obededom with their brethren, threescore and eight; Obededom also the son of Jeduthun and Hosah to be porters:

And the king made of the almug trees pillars for the house of the LORD, and for the king’s house, harps also and psalteries for singers: there came no such almug trees, nor were seen unto this day.

And there went up some of the children of Israel, and of the priests, and the Levites, and the singers, and the porters, and the Nethinims, unto Jerusalem, in the seventh year of Artaxerxes the king.

And the singers the sons of Asaph were in their place, according to the commandment of David, and Asaph, and Heman, and Jeduthun the king’s seer; and the porters waited at every gate; they might not depart from their service; for their brethren the Levites prepared for them.