Also of interest may be just about any of the cute, quirky, Rube-Goldberg-like creations from Gieskes: 
 - https://www.youtube.com/watch?v=ybopzDfrZ08
 - https://www.youtube.com/watch?v=0sA_IcICKxU
 - https://www.youtube.com/watch?v=CpRYWuRCdLw
 - https://www.youtube.com/watch?v=53J1hEXsovg
 - https://www.youtube.com/watch?v=eFX4WeXa21k
 - http://www.gieskes.nl/
 - https://www.youtube.com/watch?v=lf_rmr5Arbs
 - https://www.youtube.com/watch?v=Diix7VTdwdM
 - https://www.youtube.com/watch?v=JsPBkBx3YpA
 - https://www.youtube.com/watch?v=sTeNfms0lX4
 - https://www.youtube.com/watch?v=Laj57aAuZKw
Were there supposed to be links, e.g., to that website explaining how to drive stepper motors?
In this video, I think that the author did a pretty good job of giving a very high level overview while still hitting some of the technical details.
that's just my opinion, and maybe it is easier for me to feel that way because I'm already aware of (or have done) a lot of what the author is talking about, so seeing the thought process is enough for me to grok the rest of the project without more detail... if I knew less I might not feel that way. But then, at that point, I probably wouldn't be in a position to carry out a project like that, so detailed instructions wouldn't be super helpful anyhow.
Perhaps I'm not the target audience, but you seem to make the assumption that the viewer is familiar with the use case for this device. What I was able to gather from the video is that this device allows you to generate triggering audio/midi (?) in a more "organic" way than with something like a drum pad?
So in this case, the disk is a bit more complex than just using a clock and some switches to send out a trigger signal, -- it's less reliable and less precise.
But those are positive traits because it's easy enough to get a reliable, precise sequencer.
For what it's worth, all this device is sending out is a trigger pulse, which can be hooked to anything that would find a pulse like that useful... that's what is cool about modular synths.
So you could use it to "trigger audio" by hooking that trigger pulse to an envelope generator, but you could just as easily hook it to the "reset" of another sequencer and have it start a sequence over with every pulse. Or you could hook it to a flip-flopping swithc and have it, say, turn on and off the reverb in time with whatever is on the disc...
it's a really fun (albeit expensive) way to make music.
This seems like it would be a great project to build with a kid.
But sure. Art. It's a piece of kinetic sculpture....