Boyd’s Bible Dictionary:
(minister). A musician employed, or strolling (1 Sam. 10:5; 16:16; 2 Kings 3:15). Professional mourners (Matt. 9:23).
Concise Bible Dictionary:
The word nagan signifies a player on a stringed instrument, a harpist, though used of players of any musical instrument. Elisha once when solicited to give advice asked for a minstrel to be brought, and “when the minstrel played, the hand of the Lord came upon him” (2 Kings 3:15). The minstrels mentioned in Matthew 9:23 were pipers or flute-players hired to assist in mourning.