Numbers 18:23 "But the Levites shall do the service of the Tent of Meeting"

The service of the Levites in the Beit HaMikdash involves many different jobs.

Among them is closing the Temple gates.

They are also commanded to play musical instruments and sing in harmony with the service in the Beit HaMikdash.

To this very day, some of the same songs which the Levites sang are recited in our prayers.