פירוש על דברי הימים ב 34:12

to direct - Heb. לְנַצּחַ, lemestriyer, to direct, supervise, and so (Ezra 3:8): “to direct (לְנַצּחַ) the work of the House of the Lord,” and likewise (above 2:17): “and six hundred overseers (מְנַצּחִים) .”

and the Levites, all who were expert - Heb. מֵבִין. The term expertise (הֲבָנָה) is universally mentioned regarding song, and so above (I Chron. 25:8), when they cast lots, it is written: “like the small one so the great one, expert (מֵבִין) with pupil.” And likewise, (ibid. verse 7): “trained in song to the Lord: every expert (מֵבִין),” and it is written (ibid. 15:22): “And Chananiah, the leader of the Levites, etc., because he was an expert (מֵבִין),” and he was appointed over them to chastise [them] in raising [the voice], how they should raise [their voice], because he was an expert (מֵבִין).