SCOTT JOPLIN: "DIGITAL RAGTIME." Joshua Rifkin, piano. JOPLIN: "WALL STREET RAG." George Sponhaltz conducting Southland Stingers; Ralph Grierson, piano. EMI/Angel compact disc CDC-7 47199 2. JOPLIN: "THE RED BACK BOOK." Gunther Schuller conducting New England Conservatory Ragtime Ensemble. JOPLIN: "ELITE SYNCOPATIONS." Sponhaltz conducting Southland Stingers. EMI/Angel compact disc CDC 7 47193 2. With these two CDs, Joplin's ingratiating rags jump into the laser digital era. Angel has taken the bulk of four LPs and repackaged them into these two CDs, each containing more than one hour of music. Rifkin's initial Nonesuch LPs helped to usher in the Joplin revival and his "Digital Ragtime" is the kind of respectable performances that Joplin would have loved: slow, studied interpretations that urge comparison to Chopin's mazurkas. What is missing is the earthy quality of the dance, those swaying, free and easy syncopations that gave rag its basic appeal. Yet Rifkin's performances bring out the haunting beauty of Joplin's music. Schuller and his ragtime ensemble and Sponhaltz's enthusiastic arrangements are also a bit too careful, but the happy spirits that always overwhelm Joplin's melancholy shine out loud and clear. Everything sounds fresh and easy.