MUSSORGSKY-RAVEL: "PICTURES AT AN EXHIBITION." PROKOFIEV: "CLASSICAL" SYMPHONY. PIECES BY STRAVINSKY, KHACHATURIAN AND KABALEVSKY. National Philharmonic and London Philharmonic, conducted by Leonard Slatkin. RCA Red Seal 5661-2-RC (compact disc). The clear winner in this 69-minute collection of Russian showpieces is the Mussorgsky-Ravel in which Slatkin and the National Philharmonic tour Viktor Hartmann's gallery with an enviable combination of virtuosity and verve (RCA's recording is blessedly spacious). The low point is an underfelt "Classical" Symphony in which the LPO strings fail to articulate their passage work at Slatkin's frenetic tempos. Stravinsky's "Fireworks" sets off the requisite sparks.