Move over, E. J. Dent and Alfred Einstein, and make room for a third essential Mozartean: the senior music critic for the London Times, a boisterously unscholarly scholar, and a devoted follower of the recent deluge of revivals of operatic rarities. Mann has seen performances of all but one of the Mozart juvenilia and obscurities (Dent and Einstein couldn't have), and he explores works that the earlier critics summarily dismissed, finding foreshadowings of later, greater efforts (operatic and instrumental) and tracing the prodigy's progress from solid hackdom to brilliance. Each opera, forgotten or famed, receives its own self-sufficient chapter, begun with biographical and historical notes--librettists, fickle patrons, temperamental singers--and closed with a general evaluation. In between, Mann studies and ungushingly celebrates the scripts and scores moment by moment, using generous musical examples and prose translations of all solo arias to support his exuberant, witty descriptions of what the cast and orchestra are doing: ""She dashes away, without so much as an exit aria"" . . . ""The orchestra coda begins to make a learned point, thinks better of it and collapses in activated (and unmotivated) jubiliation."" But more important than the vivacity with which he turns sounds into words--whether instrumental (""Above the popping bassoons the violins shiver furtively and the icy flute describes broken chords"") or vocal (""The result suggests a demure yodel"")--is Mann's formulation of a critical equivalent for Mozart's unprecedented injection of psychological subtleties into music. In the Boris Goldowsky manner, but with far more delicacy and variety, he shows how key changes, vocal intervals, and (his greatest contribution) instrumental echoes can color characterizations. With Mann, technical analysis and emotional responsiveness are one: for the nostalgic Countess Almaviva in ""Dove sono,"" ""Memory can turn G minor back into G major and find an even more beautiful melody for it."" Scattered among the opera chapters are brief but substantial backgroundings in the 18th-century opera conventions that Mozart transcended; scattered throughout are hints to future directors, designers, and singers. Figaro-philes may frown when Mann exalts Cosi fan tutte above the rest, and non-musicians may be frightened off by the casual shoptalk; but every student, operagoer, and record-listener, from novice to buff, can--with varying degrees of application--benefit from this delightfully definitive study.