*Minor differences ignored. Grouped by changes, with first version listed as example.
At the appointment of Aaron and his sons,.... As they shall order and direct:
shall be all the service of the sons of the Gershonites; everyone of them was to take their share, as Aaron and his sons should appoint them:
in all their burdens, and in all their service; what each of them should carry, and in what they should perform duty:
and ye shall appoint to them in charge all their burdens; charge them carefully to keep all that were committed to them to bear, that none be lost, not a pin nor a cord.
Their service was to be performed "according to the mouth (i.e., according to the appointment) of Aaron and his sons, with regard to all their carrying (all that they were to carry), and all their doing." - "And ye (the priests) shall appoint to them for attendance (in charge) all their carrying," i.e., all the things they were to carry. בּמשׁמרת פּקד, to give into keeping. The combination of פּקד with בּ and the accusative of the object is analogous to בּ נתן, to give into a persons' hand, in Genesis 27:17; and there is no satisfactory reason for any such emendations of the text as Knobel proposes.
*More commentary available at chapter level.