How many great thanksgiving choirs did Nehemiah appoint for the wall's dedication?

Answer: Two

Two great choirs went opposite ways along the top of the wall and then stood together in the house of God.

“Then I brought the leaders of Judah up on the wall, and I appointed two great thanksgiving choirs. One was to proceed along the top of the wall to the right, toward the Dung Gate.”— Nehemiah 12:31 (BSB)