When does a song become a phenomenon? In the case of this troubadour, when a sunny, strummy demo from his 2005 EP, Extra Credit, sweeps YouTube, inspiring over 300 different tributes from as far away as the Philippines. A polished version of the track will appear on his May 13 CD, We Sing. We Dance. We Steal Things. In the meantime, fans can stream Mraz’s new, live take on the tune from a recent concert in Amsterdam.