Charles Ellicott Commentary 2 Chronicles 30:21

"And the children of Israel that were present at Jerusalem kept the feast of unleavened bread seven days with great gladness; and the Levites and the priests praised Jehovah day by day, [singing] with loud instruments unto Jehovah." — 2 Chronicles 30:21 (ASV)

Kept the feast... with great gladness. — See 1 Chronicles 13:8; 1 Chronicles 15:16 and following, 1 Chronicles 15:28, and similar passages.

And the Levites. — With stringed instruments.

And the priests. — With clarions.

Praised. — Were praising; throughout the seven days’ festival.

Singing. — Omit.

With loud instruments unto the Lord. — With instruments of strength to Jehovah. This curious phrase apparently means instruments with which they ascribed strength to Jehovah; that is to say, with which they accompanied their psalms of praise. (Compare the many psalms which glorify the strength of the God of Israel—for example, Psalms 29:1, Ascribe unto Jehovah, ye sons of God, ascribe unto Jehovah glory and strength.)

There is, however, something to be said for the Authorised Version. (Compare 2 Chronicles 5:12–13; 1 Chronicles 15:28; 1 Chronicles 16:42, from which it appears that the chronicler preferred music that was loud and strong.)