I Chronicles 25:7

So the number of them, with their brethren,.... Who each of them had twelve with them, as after reckoned: that were instructed in the songs of the Lord; taught how to sing them: even all that were cunning; expert and well skilled in the science of singing: was two hundred and eighty eight; for there being twenty four classes answerable to those of the priests, and twelve in each class, twelve times twenty four makes two hundred and eighty eight.

David, having settled the courses of these Levites that were to attend the priests in their ministrations, proceeds, in this chapter, to put those into a method that were appointed to be singers and musicians in the temple. Here is, I. The persons that were to be employed, Asaph, Heman, and Jeduthun (Ch1 25:1), their sons (Ch1 25:2-6), and other skilful persons (Ch1 25:7). II. The order in which they were to attend determined by lot (v. 8-31).