Jamieson, Fausset and Brown on 1 Chronicles 16:4-6

4-6. he appointed certain of the Levites to minister before the ark of the Lord--No sooner was the ark deposited in its tent than the Levites, who were to officiate in the choirs before it, entered upon their duties. A select number of the musicians were chosen for the service from the list (1Ch 15:19-21) of those who had taken a prominent part in the recent procession. The same arrangement was to be observed in their duties, now that the ark again was stationary; Asaph, with his associates, composing the first or principal company, played with cymbals; Zechariah and his colleagues, with whom were conjoined Jeiel and Obed-edom, forming the second company, used harps and similar instruments.