Trading on the fascination for all things “Turkish”, Mozart began his first oriental Singspiel in 1779-80. But with no prospect of performing Zaide in opera-starved Salzburg, he downed tools just before the final denouement, with the Christian slaves Gomatz and Zaide facing death for their attempted escape from Soliman’s harem. All that seems to be missing is the Sultan’s expected show of magnanimity and a final ensemble of rejoicing. Though by Mozart’s later standards the drama is slow-moving and oddly balanced, many numbers are glorious. Highlights include Zaide’s three contrasting arias, a ravishing “sunrise” trio, a powerful quartet foreshadowing the one in Idomeneo, and two “melodramas” that alternate speech with highly charged music.

With the libretto lost, most performances concoct brief passages of dialogue to link the musical numbers. In this new version, dialogue is omitted in favour of a racy – and over-wordy – narrative by actor Tobias Moretti, peppered with jokey-ironic topical references. Non-German speakers may be grateful for the fast-forward button. Musically, though, the performance is worth investigating. Harnoncourt is at his most sensitive, shaping the lyrical numbers affectionately yet without mannerism, and bringing his trademark explosive energy to such fiery zoological arias as Soliman’s “Der stolze Löw’” and Zaide’s “Tiger! Wetze nur die Klauen”.

Of the singers, Rudolf Schasching tends to equate vehemence with shouting. But Diana Damrau copes effortlessly with Zaide’s cruelly high tessitura and shapes “Ruhe sanft” with dreamy delicacy. At the other end of the spectrum, she rages thrillingly in the magnificent “Tiger” aria. Michael Schade makes a stylish and likeable Gomatz, though as with Florian Boesch in the role of the sympathetic harem overseer Allazim, strong characterisation can come at the expense of a true legato. In the sole aria for the comic Osmin, Anton Scharinger goes, not inappropriately, way over the top.

Paul Goodwin’s excellent recording (Harmonia Mundi, 6/98), with Lynne Dawson a rather more vulnerable Zaide than Damrau, is probably the safer recommendation, especially if you are likely to find the linking narrative a trial. But Harnoncourt and his cast do make this magnificent operatic torso a more intense and, at moments, a more disturbing theatrical experience.