If I hit the Discover tab on my Spotify page it lists "Top Recommendations" for me.
On the top line at the moment (above) are Mice Parade, Markley, Yusuf Lateef, Can, Bill Frisell, ESKA, Wizz Jones, James Yorkston, Les Ambassadeurs Du Motel De Bamako, David Lang, Quentin Sirjacq, Greg Foat, M. Ward, John Fahey and Land Of Kush.
I've heard of only seven of those names and of those I have consciously listened to just four.
Further down the same page Spotify lists albums by artists it thinks I might like based, more specifically, on my listening to Max Richter, Judee Sill, Jamie X, Led Zeppelin and the English Chamber Orchestra.
Then there are some people I might like based on my listening to people I'm not aware of having listened to at all, artists such as Tsegue-Maryam Guebro and Akira Kosemura.
If I scroll down the entire page, which contains over 300 recommendations, I would guess I have heard about twenty of them. And I've heard a lot of music.
I'm assuming that somewhere in Spotify is a digital genie, tracking the things I listen to, noting the ones that I switch away from as well as the ones I return to, until it builds up some cloud-like picture of my tolerance. In which case it seems to be doing quite a good job.
Previous experience with recommendation engines has tended to result in a menu of records either so obviously in my taste cloud that I could have thought of them myself or so popular that the only explanation for why I hadn't chosen them myself was prejudice (which is, let's not forget, always a huge part of what people do and don't listen to.) The introduction of science into the serendipitous business of musical taste has tended in the past to come up with results too broad to tempt anyone. I might like Joni Mitchell. No kidding. These Spotify results have avoided that by proffering stuff I haven't heard and taking cues from the things I listen to on Spotify, as opposed to the far broader church of things I happen to like.
Apple's competing foray into the world of streaming, announced last week, makes much of their investment in "curation" by real DJs like Zane Lowe. I'm not sure about this. Disc jockeys are the very last people I would seek recommendations from. That's because they are required by their professional code and inclined by their temperaments to pretend that there's lots of new and exciting music coming along every single week. There isn't.
The music business, together with that part of the music media that aligns itself so closely with the business that it may as well be part of it, spends all of its energies on the new, new thing. The public, on the other hand, doesn't.