> buying 24 Solenoids is quite expensive
They're about $1-2 apiece on Aliexpress; I doubt making your own can cost much less?
In my experience, making one solenoid is fun just to see how it works (and how simple it is, really); but making more than one is a little painful and not fun.
The cheapest solenoids I can see on Amazon Prime are about £5 each. 24 of those would be over £100.
Plus, the stated goal of the project is to learn a bit more about electromagnetism, so making your own solenoids is not even a bad idea.
You can learn by making one. Making 24 is super annoying IMHO.
(Also, if you want to try, ready-made sewing machine bobbins are a good alternative to 3D-printing your own solenoid body.)
And about the rest of your comment: one approach would be to buy one solenoid from Amazon, to let you do experiments and set up the whole machine, while waiting for the rest of the goods to arrive from China.
It was an insane project. He even took it on tour.
The actual build was by Eric Singer and his team.
"I used to hate electromagnetism"
As for electronic control, it shouldn't be too hard - perhaps you already know the following, but I'll write it here in case it's useful. You'll need as many electromagnetic solenoids as you have pipes. First you need to construct a 'wind chest', which is a shallow, air-tight box that can be made of any material. A plastic storage tub should do fine. Then you punch a hole in the top of the wind chest for each pipe, and make some sort of grommet to hold the pipes in place in the holes; this would be a 'toe board' on a real pipe organ. Mount the solenoids directly under the holes, and attach something soft to squish up against the pipe and stop the airflow. You of course need to have a blower that can pressurise the wind chest.
No guarantees about how that's going to sound! :) If you wanted to construct something really high-quality, you could follow Raphi Giangiulio, who has documented every stage of his fully-mechanical tracker organ: http://www.rwgiangiulio.com/index.htm
The artist is Grandbrothers and one of them is a jazz pianist and the other one is a roboticist. The latter sets up systems to control solenoids striking the strings and body of a grand piano while the former plays on the keys. It's a duet between human and machine.
But the best thing about this story is the video "Without the Xylophone" - a terrifying robotic bed of nails.
You can have a look at Daisy and Bela as well :)
But I think Arduino is a good choice for this.
1. The microcontroller isn't generating audio onboard, it's driving solenoids to hit something. Arduino can do that — the solenoids have travel time but Bela wouldn't solve that.
2. This is more like a sequence playback machine, there's no continuous real-time interactivity. Play/pause is the main interaction and a few ms is ok.
(If you wanted to duet with it latency-free the top of the xylophone is completely exposed so you can just play it normally.)
using very rapid magnetic oscillations (like a speaker??)?
I think the electronics would be different, but is it possible?
You might like the Magnetic Resonator Piano: http://instrumentslab.org/research/mrp.html
You could send a plain sine wave matching the frequency of the bar above it, but at that point you've just invented a single frequency speaker.