Albert Barnes Commentary 1 Chronicles 25:2

"of the sons of Asaph: Zaccur, and Joseph, and Nethaniah, and Asharelah, the sons of Asaph, under the hand of Asaph, who prophesied after the order of the king." — 1 Chronicles 25:2 (ASV)

Under the hands of Asaph... — That is, “under the direction of Asaph,” who himself “prophesied,” or performed the sacred services, “under the direction of the king.”