This would play MIDI files, not MP3s. Midi files are the digital version of that book with the punched holes, it's a sequence of note events over time.
The physical book with holes forms a series of air valves. So what you do to convert it is attach a bunch of pneumatic solenoid valves instead. Then there is some interface board that lets you control a bunch of solenoids from a laptop. It's not really that complicated but you need one valve for each note, so you need a lot of them, and you have to physically plumb in each one to the organ.
Have a look at Look Mum No Computer, he does this kind of stuff: https://www.lookmumnocomputer.com/projects#/joans-church-org...
These projects look awesome, if I'm ever in the UK I'll checkout their museum.
An orchestron is basically a player piano with extra instruments attached. Retrofitting for MIDI makes a lot of sense. Regular piano rolls are available for player pianos. Orchestrons were not standardized, so there's not much content available.
In the SF bay area, the carousel at the Santa Cruz Beach Boardwalk has a 1894/1911 Ruth and Sohn band organ. Recent videos show that it's had a major overhaul and now runs on MIDI.[2] So they can modernize the playlist. It's amazing that thing is still running, next to the Pacific Ocean for well over a century.
The Youtube Algorithm must be recommending similar videos to the both of us as I started getting the same kind of content a few weeks ago. I'm pretty partial to the Ace of Base "I saw the sign" cover that it's been recommending.[0]
I did a little bit of digging and found this guys website: https://www.mechanicalmusicman.com/
It would be neat to see a humanoid robot feed the tape into the machine and press play and then have the camera zoom out to a bunch of robots dancing together.
Something about robots dancing to music that's produced by a mechanical MIDI machine feels right. Like a prelude to the impending replacement of humanity.
There's a really interesting history of automata at Disney too, someone made a very good video about it here if you haven't seen it!
One of the guy’s videos shows a pile of piano rolls for the machine, and one is labeled ”Never gonna give you up” :-)
I didn't want to be too nosy but based on what I saw when I went last year it looks like it's running Windows 90-something with an ancient interface but clearly it works for their purposes! They use it to demo the machine several times a day.
It just plays notes; those notes are sourced from MIDI files (though they could also be sourced from a MIDI keyboard or similar, so a human can play the machine live).
The MIDI data stream, at it's most simple basis, is just a series of "note on" and "note off" commands. (MIDI can additionally do a lot more than this, but let's not dwell on that.)
This concept actually compares particularly well with what a punched paper roll accomplishes: That, too, is just a series of "note on" and "note off" commands. For every possible note or drum or percussive (or automaton) thing the machine playing the paper roll can do, there's either a hole in the paper ("on") or there is not ("off").
One system is digital and happens in numberland with circuits and/or code, while the other is pneumatic and uses valves and pipes and pumps to get the work done.
But they're both binary systems, so it can be pretty straight-forward to convert between the two.
Relatedly: A somewhat aloof chap in England has found himself with a fondness for pipe organs. He scored a whole church organ from a lady's house, converted it to MIDI with a rather grand assortment of custom PCBs and rewiring, and put it in his museum. (That organ was designed to use electricity and solenoid valves, and meant to be played live instead of with a paper roll, but it's the same game: Binary is binary.)
The process is documented here: https://www.lookmumnocomputer.com/joans-church-organ
https://www.youtube.com/watch?v=2GcmGyhc-IA
Basically, you have some pedals which generate a vacuum, and then everything is powered and controlled via vacuum. (The internet may not be a series of tubes, but a player piano literally is.)
Using vacuum to control things may seem very niche and exotic, but it was actually very common. Basically every car engine up through about the 1980s used vacuum to control the engine. Cars with a mechanical ignition system often used a vacuum advance to adjust the timing at higher RPMs, for example. Early cruise control systems used vacuum to adjust the throttle.
Anyway, all pianos have felt hammers which strike the string. When you're playing the piano manually, there's a mechanical linkage between the key you press and its hammer. In a player piano, there's another way to move the hammer: a vacuum controlled actuator. The piano roll has holes in it corresponding to notes. The holes allow air to pass through, and that causes the actuator to push the hammer into the string.
In that dance hall machine, which appears to be essentially a pipe organ, there are some similarities and some differences. A pipe organ works by blowing air through the pipes. There's a "wind chest" that stores pressurized air, and when you press a key on the keyboard, it opens a valve to let air into a particular pipe. In the old days, that linkage (between the key and the valve) was mechanical. These days it's electrical or electronic.
At the end of the video above, he even briefly mentions a band organ (which is similar to a dance hall machine) and how music rolls work for it, and it's a similar vacuum system to a player piano.
So I believe a dance hall machine with a music roll probably uses a combination of vacuum and positive pressure. The vacuum would allow reading the music roll (the paper with holes in it corresponding to notes), and that vacuum would actuate valves that allow positive pressure air into the pipes to make sound. In order to convert one of those to be controlled electronically, you could use a bunch of solenoid valves to either control the vacuum or directly control the air going into the pipes. I'm not sure which way they do it.
