This engrossing documentary traces the rise and fall of Napster, the free file-sharing service that revolutionized music consumption, ran afoul of the record industry, and became a test case in copyright law. Writer-director Alex Winter focuses on the partnership between Shawn Fanning and Sean Parker, who founded Napster in 1999, and the excitement of discovery and entrepreneurship is almost as potent here as in The Social Network (in which Parker figured as a character). But Winter is thorough as well, collecting a variety of opinions from musicians, record industry executives, and legal experts when the story turns to the copyright infringement suits filed against Napster in 2000 by Metallica and the Recording Industry Association of America. When Napster filed for bankruptcy two years later it created what one company insider refers to as “a $500 million sinkhole,” but it had opened up a national debate about what file-sharing means for artists, listeners, and the businessmen who always manage to get between them.