Bobby Osborne, the lead singer and mandolinist of the Osborne Brothers, a group that broadened the commercial appeal of bluegrass music and recorded two of the genre’s most enduring standards, “Rocky Top” and “Ruby, Are You Mad?,” died June 27 at a hospital in Gallatin, Tenn. He was 91.
His son Bobby Osborne Jr. confirmed the death but did not give a cause.
Mr. Osborne was one of the last living musicians from the genre’s first generation, having begun his career in the late 1940s as a guitarist with the Lonesome Pine Fiddlers. He was also the Grand Ole Opry’s oldest regular performer at the time of his death; he joined the show’s cast with his brother Sonny in 1964 and last appeared on its stage on May 19.