en_tn/neh/12/46.md

there were directors of singers

This sentence gives us more information about the time when David told people how to worship at the temple.

In the days of Zerubbabel

Zerubbabel was a descendant of King David and one of the governors in the region of Judah.

They set aside the portion

"All Israel set aside the portion"

gatekeepers

See how you translated this in Nehemiah 7:1

the descendants of Aaron

This refers to the priests in Israel, who descended from Aaron, the brother of Moses.