Moses und Aron review – unmissable, rare Schoenberg opera

Schoenberg's only full-length stage work stands alongside Berg's Lulu, Puccini's Turandot and Busoni's Doktor Faust as one of the great unfinished operatic projects of the 20th century. Unlike those works, though, Moses und Aron is almost always performed nowadays as Schoenberg left it when he abandoned the score in 1932, with only two of the planned three acts completed.

Like Schoenberg's other great biblical work, the oratorio Die Jakobsleiter, it has remained a tantalising torso, which only rarely reaches the stage. Welsh National Opera's production is only the second by a British company; the work received its UK premiere at Covent Garden in 1965, conducted by Georg Solti and directed by Peter Hall, and was revived there once. Since then, it has only been heard here in concert performance, so WNO's enterprise and success in presenting this fascinating but hugely challenging piece should not be underestimated.

Jossi Wieler and Serge Morabito's production originated at Stuttgart in 2003. They update the biblical story to what seems to be the Middle East today; Anne Viebrock's design is a conference chamber where, presumably, some kind of political deal is to be thrashed out. The first-act argument about means and ends between Moses and his brother becomes a battle of ideologies, and when in the second act Moses goes off to collect the commandments, the "wilderness" in which he leaves his people is a cinema – in which Aron screens what are presumably violent and pornographic films in an attempt to gain their support. There's no golden calf, let alone a dance around it, and no orgy to speak of, except some rather desultory couplings around the cinema seats.

Such a treatment does a work that hovers uncertainly between opera and oratorio no favours, and certainly it's the powerful music rather than the drama that comes across most strongly here. WNO's Lulu last year showed that Lothar Koenigs is a wonderfully accomplished conductor of the Second Viennese School, and every layer of Schoenberg's orchestral score emerges with total clarity and sincerity. The surging Mahlerian string line that underpins Moses' despair at his inability to communicate is a hair-raising close, while moments of chamber-like intimacy and dionysiac abandon are beautifully contrasted.

Sir John Tomlinson is the wonderfully contained, anguished Moses, delivering Schoenberg's Sprechgesang with total naturalness. The suave, plausible Aron was Mark Le Brocq, whose performance had so much assurance and authority it was hard to believe that he is the understudy, and had only known he was appearing a few hours earlier. And at the centre of it all is the WNO Chorus, delivering Schoenberg's ferociously tricky writing as if they have been doing it all their lives; together with the orchestra they provide the foundation on which this unmissable musical achievement is based.