CLASSICAL Strauss, Richard: ''Don Juan''; ''Till Eulenspiegel's Merry Pranks''; ''Death and Transfiguration.'' Detroit Symphony Orchestra, Antal Dorati, conductor. (London digital LDR-71025) - The performances on this disc are very fine. Dorati's account of ''Death and Transfiguration'' is particularly well conceived and executed. But what sets this release apart is the utter beauty of the recording itself. I cannot remember when an orchestra has been more sumptuously recorded. The Detroit holds up to the cruel scrutiny of the microphone, revealing a very fine ensemble with few weaknesses and numerous strengths. It may not give the Berlin Philharmonic a run for its money, but it is clearly a fine ensemble, which Dorati restored to fine condition during his brief tenure as music director. Sound fans take note, and Strauss fans, too, for Dorati's restraint is rather appealing for a change in music that often becomes at best overinterpreted or at worst overwrought.