I saw this for the first time today. Faircamp crawls an audio library and generates a static website for streaming the files. Some web hosts offer it as a service now as well. It’s for artists who allow people to download music for free, but with the option of donating money. Looks pretty simple for those who have basic command-line skills. It’s free and open-source. (And not to be confused with the music festival.)
Here’s a setup guide: