''Rejuvenated'' was the word chosen by Michael Oliver when Brendel's oldish recording of the Impromptus reappeared on CD this April. Even before looking up that review I had reached the same conclusion. The sound seems less plummy while retaining its old warmth. Yet I still think Lupu's piano emerges even more clearly and purely—if only because totally free of all background. On the Brendel CD (re-mastered from original analogue recordings) the keenest ear may note just a trace of his emerging from the speaker. Musically, it's impossible to make a clear-cut recommendation. Maybe Brendel's Schubert is slightly more volatile, Lupu's more equable. But both artists make you fall in love with him all over again.'