Did this guy also have a deal with your parents using painted coins? The juke box owner would supply the diner owner with a number of painted coins. (Often red nail polish would be used.)
When the box had been quiet too long, the diner owner would put one of the painted coins in the machine to encourage patrons to start feeding the machine. When the juke box guy cleared out the coin box, the painted coins would be returned to the diner owner. Lather, rinse, repeat.
Sometimes these coins would enter general circulation. I even got one not too many years ago.
As I recall from my experience with them some decades past, they aren’t very loud, so noise bleed wasn’t a big deal. Preteen me thought they were the coolest thing
I remember restaurants with the jukebox selectors at each table, I still eat in one but sadly the jukebox stuff was taken out years ago.
It now occurs to me how much expense and wiring it would have been to install a system like that. There were no touchscreens, no wireless. The box on the table would have been a bunch of buttons and the rotary spinner with paper song info cards that they had to manually load and keep updated. Update one song, have to change it at every table. And there would have to be wiring from each table to the jukebox.
My guess is that the wiring was a daisy chain from one table to the next, perhaps using cheap 4-wire telephone cable, with wires one or more groups of tables going to the main box. There didn’t have to be one wire from each table to the box.
Here is the service manual for a Seeburg Wall-O-Matic. 3 wire interconnect, two for power and one for pulse code modulated control signals. A motor in the Wall-O-Matic provides the timing for the PCM signal. Up to 6 Wall-O-Matics can be connected on a single cable run. More Wall-O-Matics require supplemental power supplies (I assume they can share the same PCM bus). The PCM bus is connected to a vacuum tube receive amplifier in the master Select-O-Matic.
Bus contention (users at one or more Wall-O-Matics entering selections at the same time) would be a problem and lead to unexpected selections.
I was in one of those places once. It was a retro themed diner with a totally RAD jukebox, . The devices at the tables weren’t jukeboxes, they were simply devices one used to pay for and select. If people ordered tunes at their devices before you, you had to wait until their tunes played before the tunes you ordered spun up just as you would if everyone chose and paid at the main device.
The one place I’ve eaten at, in the late 70s or early 80s, that had functional ones, I could swear that it played at the table. They were updated with contemporary songs in my case. Although I can’t be absolutely certain that it played at the table, even though I seem to recall it thus, because the couple of times we used it, it was not very crowded so we didn’t have to worry about other people hearing, nor conversely, selecting songs before us.
EDIT: even by the early 80s, a quarter was worth more than a dollar today, so it was as expensive as buying something in a vending machine, so I can see how people made some money on it in places it was popular despite the hassle.