The following musicians of the Levite clan of Asaph were in the places assigned to them by King David's instructions: Asaph, Heman, and Jeduthun, the king's prophet. The guards at the Temple gates did not need to leave their posts, because the other Levites prepared the Passover for them. 1
References for 2 Chronicles 35:15
35.15 1 Ch 25.1.