He is currently working on the 3rd evolution of the marble machine and posts build updates on this YouTube channel. Interesting intersection of music and machining content.
His videos are often entertaining (he's very charismatic and enthusiastic), and you'll learn a decent amount about engineering. But the most important thing that you'll learn are the unstated lessons: the necessity of compromise and the importance of setting measurable and realistic goals if you ever hope to actually achieve a given result. Though if nothing else, I applaud him for being so open with his efforts, especially when things don't pan out like he was expecting.
The consequence of that is that it has to be reliable enough to play through a full concert without maintenance or breakdown, and it has to be robust enough that it can be transported from place to place. These are his hard requirements.
Then there are some less well defined requirements. Which is that the machine has to play nice music and has to be a marble machine as Martin understands it.
This last is the real constraint. Otherwise he could just buy a midi keyboard which would fulfil all the requirements about reliability, robustness and quality of music, but would fail the spirit of the endeavour.
I agree that there Martin seems to be aiming for a very high degree of repeatability in timing, but it also seems that he has designs which meet those expectations of his and this was not the reason why he abandoned the second attempt. (Ad far as i can tell based on the videos.)
Many of the digital sequencing and notation products I've worked with went out of their way (arguably) to play "less-tight music" through various "humanizing" features.
Yes, we want music that is sufficiently accurate and "tight"... but within the confines of human capability. The slight errors of both time and intonation in some cases give music a much more human feel. Now to be fair, I don't want to suggest that this sort of human inaccuracy is mere randomness either: it's typically not just random error... there's usually a bias and it definitely within limits (unless you're a bad musician of course :-) ).
Super-tight MIDI music sticks out like a sore thumb when you mix it with things performed by humans.
https://www.youtube.com/watch?v=WN90HYiFpAw
Some people will say it's common-sense stuff but it is stuff I see everyday writing software and it's so hard to change. It's refreshing to see a spaceship company having the same issues haha.
This is how I felt at first, and I appreciated (and still appreciate) the frankness of his verve for experimentation. But by this point I wouldn't use the word "speedrunning" to describe his progress; he appears to have found the practical limits of autodidactism. If his only goal in life was to produce the machine (which, to be clear, it isn't), then it would have been much faster to go to school for a few years and get a degree in engineering, while apprenticing as a machinist on the side. His publicly-broadcast education, while entertaining, is anything but efficient.
I really loved his series building the second one, but when he decided that it was fundamentally flawed and he needed to rebuild from scratch, I stopped watching in frustration.
He's really talented, but I'm just... sad for him.
A kind old hand took me aside and taught me about KISS (Keep it Simple) and it must be good enough.
You really need to be able to evaluate if something is worth your time and it’s often best to just try what exists and only iterate if needed. Especially when you actually need to deliver a product
Following Martin's journey has been a privilege. His honest insights on the struggle of trying to balance hard design requirements with keeping that which made the original project fun and playful have been insightful and fascinating.