“The list of those who did the work and of their duties included the sons of Asaph. Zaccur, Joseph, Nethaniah, and Asarelah were the sons of Asaph, under the direction of Asaph. They prophesied under the direction of the king.”
Asaph was from the Gershonites. There are 2 other people with the name of Asaph. Some Psalms (73-83) are attributed to this Asaph as well as this group of singers who called themselves the sons of Asaph. The 4 sons of Asaph also prophesied under the direction of Asaph and King David. (1) Zaccur is a name that appears 4 other times. (2) Joseph was, of course, the son of Israel who brought the Israelites to Egypt. However, there were over 20 biblical people with this same name. There were 3 other people with the name of (3) Nethaniah. (4) Asarelah only appears here and nowhere else. These prophetic singers were under the king and not free lance prophets.