en_tn/2ch/30/21.md

kept the Festival of Unleavened Bread

Here "kept the festival" is a idiom meaning to participate in the festival or celebrate the festival. Alternate translation: "celebrate the festival" (See: rc://en/ta/man/jit/figs-idiom)

singing with loud instruments to Yahweh

"singing and playing loud musical instruments to Yahweh"