Tripping on LCD

TRIPPIN ON LCD: Members of Arcade Fire joined LCD Soundsystem on stage at Madison Square Garden Saturday night, handling background vocals on the song "North American Scum." The group’s farewell concert was preceded by four performances at New York's Terminal 5. LCD frontman James Murphy introduced Arcade Fire's Win and William Butler and Régine Chassagne with an explanation of how the band has its roots in both Canada and the U.S. LCD Soundsystem announced their retirement on February 5. In recent years, Murphy has expanded into film work, arranging and scoring the soundtrack to 2010's Greenberg. (4/4a)