Classical string quartet covers Willie Dixon tunes! But then the Kronos Quartet is already famous for a genuinely rockin' homage to Jimi Hendrix's ''Purple Haze,'' so its version of Dixon's ''Spoonful'' on its latest album, Short Stories is notable mainly because the damn thing sounds so classical. Which is no criticism. Kronos proved its versatility long ago, with performances that opened the concert hall to everything from rock to African music. If it wants to produce an abstract meditation on ''Spoonful,'' rather than a literal rendering, well, by now that seems more adventurous than playing the song as straight-ahead R&B.
The rest of the album works best when Kronos unveils other surprises, like the recorded voice of journalist I.F. Stone, subtly transformed by composer Scott Johnson into thoughtful, liquid music. Not every cut is persuasive; John Zorn's ''Cat O' Nine Tails,'' meant to be a collection of cartoon-style fragments, stops dead at the end of each one. But if classical music should ever become contemporary art, Kronos is pointing the way. B