“Didier Marouani, a disco star who first toured the Soviet Union in 1983, and his lawyer, Igor Trunov, were detained Tuesday evening in a bank where they said they planned to sign an out-of-court settlement with Filipp Kirkorov, Russia’s biggest pop star. Marouani, 63, claims one of Kirkorov’s songs, “Cruel Love,” contains music he wrote years before.”