Because bringing the ark of the Lord into Jerusalem is such an important event, David instructs the Levites to go all-out with their music making to worship the Lord. They should play “loudly” on their instruments and “raise sounds of joy”. (v. 16) For those who love Him, to worship the Creator is a pleasure, and we should make known how great and awesome He is. There is also the practical consideration that there will be a great many people on the move while the ark is being transported. Without digital amplifiers or anything, the only thing they can do to try to help everyone hear is to just be louder. More instruments, more singers, more music!
The musicians are divided up by their instrument, and the names of the leaders of each section are given. Harps, lyres, cymbals, and the trumpets played by the priests are all mentioned in this chapter. Special mention is also made about Obed-edom (who had been taking care of the ark since the Lord broke out against Uzzah) and Jeiel (and/or Jehiah?) were the gatekeepers for the ark. I take this to mean they were in charge of the Levites who would actually carry the ark on the poles as they walked, and also keep anyone else from coming near and bringing down the wrath of God upon them. They probably didn’t carry the ark themselves, because they were given lyres to lead with, and you can’t play a lyre and carry poles at the same time.
David, the elders of Israel, and the leaders of the armies all went along with the Levites and priests to escort the ark to Jerusalem. Seven bulls and seven rams were sacrificed on the altar to thank the Lord for giving the Levites safe passage while they carried the ark. All the people were worshipping God with joy, and David was dancing among them, but his wife Michal, Saul’s daughter, despised him for acting the fool, as she thought it. The Chronicler doesn’t go into the details, but merely emphasizes that Saul’s bloodline did not follow the Lord as closely as David did.
You deserve our most emphatic, enthusiastic worship. Your glory cannot be contained.