Bluegrass music lost one of it pioneers when Earl Scruggs, who developed the modern banjo sound, died yesterday at the age 88. Scruggs and his guitar-playing partner, Lester Flatt, were best known for songs such as "Foggy Mountain Breakdown" and "The Ballad of Jed Clampett." Flatt and Scruggs were regular guests on the Grand Ole Opry and were heard on the Opry's popular radio broadcasts on WSM.