“King David and the officers of the army also set apart certain of the sons of Asaph, Heman, and Jeduthun for the worship service. They should prophesy with lyres, with harps, and with cymbals.”
As mentioned earlier in chapter 6 of this book, King David was associated with songs, music, and psalms. Thus it does not seem strange that he should appoint Levites to sing songs in the house of Yahweh. The problem is that the house of Yahweh was only established under Solomon. Therefore, this section talks about songs around the tabernacle in the tent of meeting. However, once the temple was complete, they performed there. The 3 people in charge were Asaph, Heman, and Jeduthun. Earlier in chapter 6 it was Ethan rather than Jeduthun who was in charge. The other 2 people are the same as the 2 mentioned in chapter 6.