Here, legendary opera soprano Maria Callas deserves coauthor's credit with Callas-expert Ardoin (The Callas Legacy, 1977); this is, after all, Ardoin's energetic transcription and interpretation of Callas' own instructions--preserved on audio tape--to students at Juilliard in the early 70's. A general prologue, patched up from the singer's taped remarks and some interviews, ushers in the record of the actual lessons, in which arias from Mozart, Rossini, Verdi, et al. are dissected note-by-note with astonishing insight. (""Mozart is usually sung with too much delicacy, as though the singers were on tiptoes, when his music should be performed with the same frankness and bel canto approach one would use in II trovatore, for example."") For opera lovers, then, a pedagogic delight.