The music streaming revolution is in full swing, and Spotify remains its talisman.

The Swedish start-up recently announced that it had secured 10 million paying customers - around double the global paying subscriber audience of rivals Deezer (5m) and Rdio (6m). (A rough but thoroughly fair calculation: if all of those Spotify customers were to pay the company’s standard £10 per month bill, it would amount to a cool £1.2 billion in revenue each year - and that’s not counting ...