I don't have a good article to link to at the ready, but if you're interested in this, you may be interested in 1-bit music synthesis. (at a normal (48k) sample rate -- I don't mean doing PDM in the Mhz range and then using a LPF) It's extraordinarily limiting, and yet, skilled hackers have been able to make music, even polyphonic music(!)
This is most likely absolutely useless knowledge & at the same time really interesting exploration of how some technical limitations affect the work process. It's a very original-meaning hacker spirit article, the kind I'd expect to find on slashdot circa 1997.