The sad death of Leonard Ingrams last year deprived Garsington Opera of its founder and moving spirit. However, it would be hard to imagine a more suitable tribute to him than John Cox's splendid production of Der Stein der Weisen (The Philosopher's Stone) which opened on Tuesday night.

Ingrams knew the historical Vienna really well, and the opera (of 1790) is a fascinating example of the city's unique vein of late 18th-century fantasy. Of course, its interest has always been supposed to be in the fact that some of it is certainly by Mozart, and the slightly absurd allegorical tale bears more than a passing resemblance to The Magic Flute. It was, in fact, commissioned by The Magic Flute''s impresario, Emmanuel Schikaneder, with the score cobbled together by at least four named composers, of whom Mozart was merely the best-known at the time.

The result, in terms of theatre, is a slightly mad comic fantasy, sometimes like J.K.Rowling, but set in the 18th century, more often like The Magic Flute seen entirely through the eyes of Papageno. As in that work, both the good and evil principles of the universe appear, the latter as a rich comic character (the excellent Michael Druiett), the former with bursts of unexpected coloratura, well delivered by Iain Paton. The 'serious' pair of lovers lack the grandeur of the Magic Flute music, but the Papageno/Papagena equivalents (Leigh Melrose and Teute Koo) were irresistible, the latter stealing the show almost non-stop, whether looking helplessly out of the pyramid in which she is imprisoned in Act I, or transformed into a cat in Act II (this is the well-known 'miau-miau' duet, one of the few pieces which is most certainly by Mozart).

This latter point illustrates what is surely the most striking quality of this opera. Mozart or not makes little difference what we have here is a breathtaking sophistication of musical language. This is the lingua franca of the Vienna in which the young Beethoven was about to appear, and the performance reminded one that his work of the 1790s may well have been inspired at least as much by Mozart's collaborators on this project Henneberg, Schack et al as by Haydn or indeed Mozart himself.

That said, we were faced with a second-half which had one half-consciously yearning for the sublimities of The Magic Flute (see how the great drives out the good!). But the show was rescued by John Cox's inspired direction (his integration of dancers into the action particularly masterful), not to mention Steuart Bedford's conducting and musical arrangement. Normally, I would look askance at the sudden interjection of Mozart's sublime Masonic Funeral Music into this farce but then I thought, why not? He would have done just that. Enthusiastically.