en_tn/2ch/07/06.md

each standing where they serve

"each standing in their appointed place"

the Levites also with instruments of music of Yahweh

The word "stood" is understood from the previous phrase. Alternate translation: "the Levites also stood with instruments of music of Yahweh" (See: rc://en/ta/man/jit/figs-ellipsis)

For his covenant faithfulness endures for ever

The abstract noun "faithfulness" can be stated as "faithfully" or "faithful." See how you translated "covenant faithfulness" in 2 Chronicles 7:3. Alternate translation: "God will always be faithful to his covenant with us" or "God will always faithfully love us" (See: rc://en/ta/man/jit/figs-abstractnouns)

all Israel

This generalization refers to those who were at the feast in Jerusalem, not necessarily to every person who lived in Israel. (See: rc://en/ta/man/jit/figs-hyperbole)