All these who were chosen to be gatekeepers at the thresholds were 212. These were enrolled by genealogy in their villages, whom David and Samuel the seer appointed in their office of trust. Verse ConceptsSeersVillages

Then David spoke to the chiefs of the Levites to appoint their relatives the singers, with instruments of music, harps, lyres, loud-sounding cymbals, to raise sounds of joy. So the Levites appointed Heman the son of Joel, and from his relatives, Asaph the son of Berechiah; and from the sons of Merari their relatives, Ethan the son of Kushaiah, and with them their relatives of the second rank, Zechariah, Ben, Jaaziel, Shemiramoth, Jehiel, Unni, Eliab, Benaiah, Maaseiah, Mattithiah, Eliphelehu, Mikneiah, Obed-edom and Jeiel, the gatekeepers. read more.
So the singers, Heman, Asaph and Ethan were appointed to sound aloud cymbals of bronze; and Zechariah, Aziel, Shemiramoth, Jehiel, Unni, Eliab, Maaseiah and Benaiah, with harps tuned to alamoth; and Mattithiah, Eliphelehu, Mikneiah, Obed-edom, Jeiel and Azaziah, to lead with lyres tuned to the sheminith. Chenaniah, chief of the Levites, was in charge of the singing; he gave instruction in singing because he was skillful. Berechiah and Elkanah were gatekeepers for the ark. Shebaniah, Joshaphat, Nethanel, Amasai, Zechariah, Benaiah and Eliezer, the priests, blew the trumpets before the ark of God. Obed-edom and Jehiah also were gatekeepers for the ark.

He appointed some of the Levites as ministers before the ark of the LORD, even to celebrate and to thank and praise the LORD God of Israel: Asaph the chief, and second to him Zechariah, then Jeiel, Shemiramoth, Jehiel, Mattithiah, Eliab, Benaiah, Obed-edom and Jeiel, with musical instruments, harps, lyres; also Asaph played loud-sounding cymbals, and Benaiah and Jahaziel the priests blew trumpets continually before the ark of the covenant of God.

So he left Asaph and his relatives there before the ark of the covenant of the LORD to minister before the ark continually, as every day's work required; and Obed-edom with his 68 relatives; Obed-edom, also the son of Jeduthun, and Hosah as gatekeepers. He left Zadok the priest and his relatives the priests before the tabernacle of the LORD in the high place which was at Gibeon, read more.
to offer burnt offerings to the LORD on the altar of burnt offering continually morning and evening, even according to all that is written in the law of the LORD, which He commanded Israel. With them were Heman and Jeduthun, and the rest who were chosen, who were designated by name, to give thanks to the LORD, because His lovingkindness is everlasting. And with them were Heman and Jeduthun with trumpets and cymbals for those who should sound aloud, and with instruments for the songs of God, and the sons of Jeduthun for the gate. Then all the people departed each to his house, and David returned to bless his household.