The Jews rebuilt the wall of Jerusalem under the leadership of Nehemiah, and they celebrated the occasion,

So the two thanksgiving choirs stood in the house of God, likewise I and the half of the rulers with me; and the priests…The singers sang loudly with Jezrahiah the director (Nehemiah 12:40–42).

The Jews sang loudly because they were happy that the protective wall around Jerusalem had been rebuilt.

For what things should Christians sing loudly?