ESV Study Bible explains:
1 Chron. 25:1–8 David and the leaders of the Levites divided the musicians into the three family groups of Asaph, Jeduthun, and Heman (see 6:31–47), who prophesied with musical instruments, i.e., wrote songs. In some cases, their songs seem to have become part of OT Scripture, for Asaph is named in the titles of Psalms 50 and 73–83, and Jeduthun in the titles of Psalms 39, 62, and 77. In addition, Heman here may be the same person as Heman the Ezrahite named in the title of Psalm 88 (cf. also 1 Chron. 6:33). The verb “to prophesy” (Hb. naba’) indicates that their songs were prompted or guided by the Spirit of God. This shows that “prophecy” is not always a direct announcement of God’s plans; it indicates that the person is operating as God’s authorized spokesman, here providing the right way for God’s people to sing to him (they prophesied . . . in thanksgiving and praise to theLord, 25:3).