Avi K, ?’ ????? ???? ???? ???? ???? ?”? ???? ?”? ?????? ????? ??. It seems that the Rav’s son in fact has preference for the position (provided that he is fit). The ??”? speaks of a case where the Tzibbur did not want the Chazan’s son, and nevertheless awards him the position.
I’d like to see the Chasam Sofer inside, if you can provide the reference. It seems like the case of the following ????, where the Mechaber says that a Minhag of the Tzibbur is tantamount to an explicit stipulation. Of course, a Tzibbur can stipulate in the Rav’s contract that his son does not enjoy automatic preference for the job, and this by-law would serve as such a stipulation.