Osvaldo Golijov, one of today’s most successful composers, is facing accusations of plagiarism. Sidereus, a nine-minute piece commissioned by a group of 35 orchestras, contains a significant chunk of music from a 2009 work by Michael Ward-Bergeman, a close friend of Golijov’s. The similarity was discovered by Tom Manoff, a music critic for NPR’s All Things Considered and Brian McWhorter, a trumpet player.