And the priests waited on their offices
 Performed them, some in offering sacrifices, others in blowing trumpets, as it may be explained from the latter part of the verse: 
 the Levites also with instruments of music of the Lord, which David the
 king had made to praise the Lord;
 under a divine direction, on which the Levites played to the songs of praise offered to the Lord, and by which they made music sacred to him: 
 because his mercy endureth for ever;
 which, as it was the close of their songs of praise, was the cause of them: 
 when David praised by their ministry;
 the songs sung being composed by him, and the instruments they played upon being of his invention, and used by his order: 
 and the priests sounded trumpets before them;
 or rather over against them, that is, over against the Levites, as they were singing and playing on the instruments of music: 
 and all Israel stood;
 while this sacred and delightful service was performing, they both stood up, and stood by the priests and Levites, and joined with them in praising the Lord.