Taylor Swift's withdrawal of her song catalogue from Spotify over royalty payments made some people question the future of streaming music. Not Sony. The shift from ownership to access is a foregone conclusion for the company. In four years, streaming and subscriptions will account for 60 percent of the music industry's $8.2 billion in revenue, Sony forecasted today. That's more than triple the 18 percent now. Where Sony and Swift agree is that people should pay for music. The popularity of free songs on services like Spotify and Pandora is the reason why streaming revenues so far have failed to offset the declines in CD sales and downloads. Sony estimates one paid subscription is worth as many as seven free music streams. For every one of Spotify's 12.5 million paid customers, four pay nothing. Getting people to pay up is the music industry's major challenge, Michael Lynton told investors at a briefing in Tokyo. He heads Sony's entertainment busine...