Used by the routine at LOWER_HALF.

Called by LOWER_HALF with its own record, whose graphic is always 11: odd, so the RET at the top is always taken and the footstep never sounds (the sessions never ran the rest). What it would play is FOOTSTEP's footstep at a fixed pitch of 128 on alternate pairs of turns, the complement of the turn counter where the robot's uses the counter itself. Knight Lore's audio_guard_wizard, where the walkers' graphics change.