He was once hailed as the next Marvin Gaye. Then, after his ripped body threatened to overshadow his music, he vanished into addiction. So what the hell was he doing recently singing his heart out in a Pentecostal church in Stockholm? And how are his abs? Amy Wallace witnessed D'Angelo's ecstatic return to the stage—and hung out with the master of the sacred and the profane as he finishes his firs