Finally, while I'm sure there's some technical reason why it wouldn't work, I personally don't see why you couldn't build an open-source, fedi-compatible midi-blogging service with a format like cohost.
Very little of the functionality there is functionality we don't (at least theoretically) have over here, somewhere. That's not to say it wouldn't be a major effort to build it, just that "tumblr, but fedi and with custom CSS" is entirely manageable.
I hope someone does it!
4/4