וְהַכֹּהֲנִ֞ים עַל־מִשְׁמְרוֹתָ֣ם עֹמְדִ֗ים וְהַלְוִיִּ֞ם בִּכְלֵי־שִׁ֤יר יְהוָה֙ אֲשֶׁ֨ר עָשָׂ֜ה דָּוִ֣יד הַמֶּ֗לֶךְ לְהֹד֤וֹת לַיהוָה֙ כִּֽי־לְעוֹלָ֣ם חַסְדּ֔וֹ בְּהַלֵּ֥ל דָּוִ֖יד בְּיָדָ֑ם וְהַכֹּהֲנִים֙ מחצצרים [מַחְצְרִ֣ים] נֶגְדָּ֔ם וְכָל־יִשְׂרָאֵ֖ל עֹמְדִֽים׃ (ס)
E i sacerdoti stavano in piedi, secondo i loro uffici; i leviti anche con gli strumenti musicali dell'Eterno, che Davide aveva fatto re, per ringraziare l'Eterno, poiché la sua misericordia dura per sempre, con le lodi di Davide per mano loro; e i sacerdoti suonarono trombe contro di loro; e tutto Israele stava in piedi.
Rashi on II Chronicles
And the priests...on their watches as David had divided them into twenty-four watches, for each watch to serve its week, and the Levites likewise on their twenty-four watches
Rashi on II Chronicles
to give thanks with musical instruments, for they recited (Ps. 136): “Give thanks to the Lord for He is good, for His loving kindness is eternal.”
Rashi on II Chronicles
with David’s praise The musical instruments with which they recited David’s praise and the thanksgivings were in the Levites’ hands.