Seeburg 222 Jukebox tube amp - remote volume control

[tubesornothing]

My brother has a 1950s Seeburg 222 Jukebox tube amp with a stereo amplifier.  We want to build a remote volume control for it. The jukebox is made for a remote volume control, its volume pot can basically be unplugged and then a a 25' cable with a pot in a handheld box can be plugged in. 

However, we want to do a wireless  remote volume control. No problem, arduino and a digital pot to the rescue! Well, not so simple:  The volume control is 25k pot with two taps on it.

See the schematic. I would like to understand why the volume pot has two taps on it.  I can see the signal gets routed to the (bass) tone control section first, then to the output section, but why the tapped pot?

Any way I can do this with a "normal" pot?  Then I can use a digital pot.

My hail mary would be to attach a little servo to pot and just control the servo.

thanks for looking.