וְעִמָּהֶם֙ הֵימָ֣ן וִֽידוּת֔וּן וּשְׁאָר֙ הַבְּרוּרִ֔ים אֲשֶׁ֥ר נִקְּב֖וּ בְּשֵׁמ֑וֹת לְהֹדוֹת֙ לַֽיהוָ֔ה כִּ֥י לְעוֹלָ֖ם חַסְדּֽוֹ׃
and with them Heman and Jeduthun, and the rest that were chosen, who were mentioned by name, to give thanks to the LORD, because His mercy endureth for ever;
Rashi
to Jeduthun The name of one of the singers, and there was also a musical instrument called Jeduthun. According to the Midrash Aggadah (Song Rabbah 4:1 [4]): concerning the edicts (דתות) and concerning the distressing laws and decrees that are decreed upon Israel.