Moreover Hezekiah the king and the princes commanded the Levites to sing praise unto the LORD with the words of David, and of Asaph the seer. And they sang praises with gladness, and they bowed their heads and worshipped. 2 Chronicles 29:30
"Although the Levites sang upon many occasions in the Holy Temple, one of their most important and basic musical tasks was the daily song. Each day, the Levite choir stood atop the platform located in the Court of Israel facing the outer altar, just inside the Nicanor Gates, and sang a special song for that particular day. On the Festivals and New Moon, different songs were sung. All of these songs, with their instrumental arrangements, were performed while the morning and evening wine libations were poured out on the altar by the officiating priests.
Thus the Levites accompanied the Divine service of the priests with a service of their own. They complimented each other; in many ways, the Levitical songs were as important a Temple function as the priestly service of the sacrifices itself, for the one could not function without the other. Each day, during the wine libation, the overseer of the choir stood atop one of the horns of the altar and signaled to the Levites “with a kerchief in his hand” to begin their song. At three points in their song, they would pause, when the priests would sound the silver trumpets and all the people in the court prostrated themselves before the Presence of G-d.
... According to tradition, the Second Holy Temple, like the first, was destroyed at the conclusion of the Shabbat — on Saturday night. Both Josephus and the Midrashic writings describe how even though the flames of destruction raged all around, and the blood of the slain flowed through the Temple, the priests nevertheless continued to serve atop the altar, and the Levites did not cease to sing, right up until the very end."