It does not appear this site streams a single music stream, rather it uses script to play a given set of music tracks.
You can see this with a program such as URL Snooper. Download and run it, and then start playing a playlist of your choice. You'll then see links in URL Snopper such as:
http://8tracks.s3.amazonaws.com/tf/003/676/264/22995.mp3
which is a particular track in a given playlist.
You'll probably also notice that such files could be downloaded to your computer and played directly.
I had a feeling someone might mention something like this. I do appreciate the replies thus far, but the point has been lost, and it's this: MC has this excellent feature - I can play audio from within a website inside it, BUT, the only way to do this is to go into Theatre Mode, and use the method described above. And silly me, yes I can use alt+tab to switch apps, but as soon as I hit the back button in MC (cos I want to look at a playlist or a photo) I lose the playing webpage.
THAT'S the issue I'm trying to resolve.
8tracks is just a side-issue, the same holds true for sbs chill which is a single stream. But perhaps I could use that snooper program to extract that particular stream and add it to a playlist.
But that still wouldn't solve the problem that a webpage will not stay open in the background.
I would rather be able to open a webpage in a tab in the standard view and have it stay open, but I can't seem to do this - I get the error message, which I also get when I open the page in Theatre View, but only for a second before the page loads anyway - this indicates some kind of inherent flaw/bug to me.
Theatre View is the current workaround to get streaming sites to work, and alt+tab is a workaround for that, and then using snooper would be a further workaround, when I can just pin 8tracks as an app tab in Firefox and it works fine.