Jay Z's Streaming Service Tidal 'Not For All'

"Our intent is to preserve music's importance in our lives," proclaimed Alicia Keys on stage at the relaunch of Tidal, a streaming music service recently bought by Jay Z for $56m. Keys was standing there not as an artist, but as an "owner" - along with other megastars like Daft Punk, Beyoncé, Calvin Harris, Rihanna and Kanye West.