All these sons of Heman, the king's seer, were given to him through the promises of God to honor him, for God gave Heman fourteen sons and three daughters.
Everything that King David did, from beginning to end, is written down in the Records of Samuel the Seer, the Records of Nathan the Prophet, and the Records of Gad the Seer.
Hezekiah had the Levites stand in the Lord's Temple with cymbals, harps, and lyres, following the instructions of David, Gad the king's seer, and Nathan the prophet. The instructions had come from the Lord through His prophets.
(In the old days in Israel, someone who went to inquire of God would say, “Come on, let's go to the seer,” because prophets used to be known as seers.)