John Gill Commentary 1 Chronicles 25

Moreover, David and the captains of the host separated to
the service
Of singing the praises of God; this was done by the princes of the people, and the chief of the priests, who were gathered together, and before whom the lots were cast, both for priests and Levites, and now here for the singers, see (1 Chronicles 22:2) (24:6) and those that were separated were

of the sons of Asaph, and of Heman, and of Jeduthun ;
or Ethan, the three precentors, or chief of the singers:

who should prophesy with harps, with psalteries, and with cymbals ;
sing psalms, hymns, and spiritual songs, indited by the Holy Spirit of God; which contained in them prophecies concerning things to come, particularly relating to the Messiah, of which there are many in the book of Psalms; and to the tunes of these they played on the above instruments of music:

and the number of the workmen, according to their service, was ;
as follows.

Of the sons of Asaph
Who were separated, and by lot appointed, to the service of singers in the temple:

Zaccur, and Joseph, and Nethaniah, and Asarelah ;
called Jesharelah, (1 Chronicles 25:14) , these had the third fourth, fifth, and seventh lots, (1 Chronicles 25:9 1 Chronicles 25:10 1 Chronicles 25:12 1 Chronicles 25:14) ,

under the hands of Asaph ;
under his instruction and authority:

which prophesied according to the order of the king ;
which Asaph composed psalms under the inspiration of the Spirit of God, and was ordered by King David to sing them, and by whose command they were inserted in the book of Psalms, where they now stand with his name to them.

Of Jeduthun
Or Ethan, the sons of Jeduthun:

Gedaliah and Zeri ;
called Izri, (1 Chronicles 25:11) ,

and Jeshaiah, Hashabiah, and Mattithiah, six ;
whereas five only are mentioned; it may be thought that Shimei, (1 Chronicles 25:17) is the sixth, he not being mentioned elsewhere; it is a tradition of the Jews, that his mother was now with child of him, and it being foreseen by the Holy Spirit that he would be the chief of a course, the number six is given, as Jarchi observes; but rather, as Kimchi, he was young, and not fit to sing, yet was chosen the head of a course, until he was grown up and fit for it; to these six came up the second, fourth, eighth, twelfth, fourteenth, and tenth lots, (1 Chronicles 25:9 1 Chronicles 25:11 1 Chronicles 25:15 1 Chronicles 25:21 1 Chronicles 25:17) and these

[were] under the hands of their father Jeduthun ;
to instruct and direct them, and appoint their service to them:

who prophesied with a harp ;
or sung a prophetic psalm or hymn on that:

to give thanks, and to praise the Lord ;
for what he had done and promised, and foretold he would do for his people.

Of Heman: the sons of Heman The third chief singer: Bukkiah, Mattaniah, Uzziel; the same with Azareel, (1 Chronicles 25:18) Shebuel; called Shubael, (1 Chronicles 25:20) and Jerimoth, Hananiah, Hanani, Eliathah, Giddalti, and Romamtiezer, Joshbekashah, Mallothi, Hothir, and Mahazioth; in all fourteen, to whom came the sixth, ninth, eleventh, fifteenth, sixteenth, eighteenth, twentieth, twenty second, twenty fourth, seventeenth, nineteenth, twentieth, and twenty third lots, (1 Chronicles 25:13 1 Chronicles 25:16 1 Chronicles 25:18 1 Chronicles 25:20 1 Chronicles 25:22 1 Chronicles 25:23 1 Chronicles 25:25 1 Chronicles 25:27 1 Chronicles 25:29) (1 Chronicles 25:31 1 Chronicles 25:24 1 Chronicles 25:26 1 Chronicles 25:28 1 Chronicles 25:30).

All these were the sons of Heman, the king's seer
The prophet of the king, as the Targum, who was frequently with him, assisting him in the words of God :
in divine things:

to lift up the horn ;
to blow with the hornpipe or trumpet, and to magnify and set forth the greatness of the kingdom of Israel, and especially of the King Messiah, the horn of salvation, that would be raised up in the house of David:

and God gave to Heman fourteen sons ;
whose names are before mentioned:

and three daughters ;
of whom we have no more account, only may observe, that both are the gifts of God, and an heritage from him, (Psalms 127:3) .