1 Chronicles 25
Like the priests and the Levites, the singers were divided by lot, designated by God's free choice. Nothing was left to the will of man: that is of all importance. The Lord's Anointed orders and the Lord decides. As for the Levites, here lots are cast for their charges, "the small as well as the great, the teacher with the scholar" (1 Chron. 25:88And they cast lots, ward against ward, as well the small as the great, the teacher as the scholar. (1 Chronicles 25:8)).
Moreover, it is under the king's direction that Asaph; Heman, David's seer in the words of God; and Jeduthun prophesy with sacred instruments — whether it be to celebrate and praise the Lord, or whether it be to exalt His power. This is one proof, among many others, that the Psalms are an inspired collection, whose character is prophetic.
In 1 Chron. 25:9-319Now the first lot came forth for Asaph to Joseph: the second to Gedaliah, who with his brethren and sons were twelve: 10The third to Zaccur, he, his sons, and his brethren, were twelve: 11The fourth to Izri, he, his sons, and his brethren, were twelve: 12The fifth to Nethaniah, he, his sons, and his brethren, were twelve: 13The sixth to Bukkiah, he, his sons, and his brethren, were twelve: 14The seventh to Jesharelah, he, his sons, and his brethren, were twelve: 15The eighth to Jeshaiah, he, his sons, and his brethren, were twelve: 16The ninth to Mattaniah, he, his sons, and his brethren, were twelve: 17The tenth to Shimei, he, his sons, and his brethren, were twelve: 18The eleventh to Azareel, he, his sons, and his brethren, were twelve: 19The twelfth to Hashabiah, he, his sons, and his brethren, were twelve: 20The thirteenth to Shubael, he, his sons, and his brethren, were twelve: 21The fourteenth to Mattithiah, he, his sons, and his brethren, were twelve: 22The fifteenth to Jeremoth, he, his sons, and his brethren, were twelve: 23The sixteenth to Hananiah, he, his sons, and his brethren, were twelve: 24The seventeenth to Joshbekashah, he, his sons, and his brethren, were twelve: 25The eighteenth to Hanani, he, his sons, and his brethren, were twelve: 26The nineteenth to Mallothi, he, his sons, and his brethren, were twelve: 27The twentieth to Eliathah, he, his sons, and his brethren, were twelve: 28The one and twentieth to Hothir, he, his sons, and his brethren, were twelve: 29The two and twentieth to Giddalti, he, his sons, and his brethren, were twelve: 30The three and twentieth to Mahazioth, he, his sons, and his brethren, were twelve: 31The four and twentieth to Romamti-ezer, he, his sons, and his brethren, were twelve. (1 Chronicles 25:9‑31) we find the different courses of singers chosen by lot and in connection with their three leaders. Asaph has only four courses of twelve men each. Jeduthun has six courses, Heman has fourteen; in all twenty-four courses composed of 288 persons. They correspond to the courses of the priesthood. Heman, "the king's seer in the words of God, to exalt his power," has the largest number of sons. His functions correspond to the glory of the kingdom, announced by prophecy and established by the word of God.