In the late '70s, the chart-topping singer/songwriter Cat Stevens formally became a Muslim, adopted the name Yusuf Islam, and after the release of his 11th and final Cat Stevens album (1978's Back to Earth), announced his retirement from the pop music business. Largely inactive during the '80s and '90s, he returned in 2006 with a new studio effort, An Other Cup, under the name Yusuf. In early 2009 he collaborated with "fifth Beatle" Klaus Voormann for a cover version of George Harrison's "The Day the World Gets 'Round." All proceeds from the song were donated to a charity to h...