> I'm sure this could be the case but I'm not convinced that their license to the content would be so specific as to require the delivery of the content video/a

> I'm sure this could be the case but I'm not convinced that their license to the content would be so specific as to require the delivery of the content video/audio together, or must be played in the foreground. Their music licenses absolutely definitely do, unless it's a paid subscription service. The music labels do not want anyone to be able to build something that might be a free competitor to Spotify. So you may only implement listening to anything you want (as opposed to a random playlist such as Pandora or iTunes Radio) if the service is a paid subscription one, probably with a minimum price point similar to Spotify, or if it cannot play audio in the background with the screen off on mobile. Licensing is a patchwork, so there's the odd exception missed, or from a VERY old deal, but that's essentially the market if you want to license music.