As much as I like the nostalgia of the good ol 1Khz Apple BEEP! there are some folks who don’t. Further, there are some games that somewhat abuse the privilege of the Apple ][ speaker.
Enter this idea… gleaned from the study of the //c and it’s clone cousin(s) from Franklin was the concept of regulating the DC voltage that the speaker output works with to produce tones.
For this to work, the +5 pin of the speaker connector needs to connect to pin 2 of J19.
The other side, pin 1, is connected to the output darlington transistor on the Apple Logic Board. As R2 is rotated, it lowers the available voltage to the speaker (the output transistor switches to ground) and there by lowers the volume.
An analog taper pot might do even better, but 50K Linear is what I had and it provides pretty even continuous control from end to end.