Here’s a link to the song Everytime (A Cappella) for you to try for yourself.

I clicked the link on my Mac, logged in to the page that appeared, and was able to listen to the song in my browser, without jumping to iTunes.

According to the Reddit comments, this seems to have appeared sometime after WWDC. It also appears that there is a 3rd party API so people can build their own web-based music players. The API might still be in beta, though I tested the above link on the public release of High Sierra.

Interesting.

UPDATE: Here’s a post from Kirk McElhearn about all this from back in June, when it first became available.