Sitting down in the audience for Swiss director Christoph Marthaler's Meine faire Dame is something akin to entering a conversation class in a language you have no knowledge of. At first, it's completely baffling and you doubt you'll ever make sense of it, but eventually, through repetition and a sensitivity to the patterns that structure the exchanges, you learn.

The stage is set as a dated-looking language lab, the type with individual booths, headphones and cassette decks on each desk, vinyl floors and wheelie chairs. Oh, and to one side there's a grand piano, and to the other an electric organ which will in time be played by Frankenstein's monstor. Of course. A pianist comes in and begins to play, and for a long time nothing else happens, until a man becomes faintly audible and sporadically visible, through a window in a closed door, shouting and cursing in a manner that would befit Basil Fawlty about having lost his slippers.

What follows is part musical, part surrealist meditation on the emptiness of language, aided by some meltingly beautiful singing, bilingual punning, and uproariously daft physical farce (Carina Braunschmidt's routine with her arm in a sling is particularly funny). Known for his obsession with ritual, Marthaler repeats certain sequences again and again, almost to the point of infuriation, then changes a little something to make a point either tender or comical. The opening scene in the language lab with its frenetic drilling of tongue twisters sets a precedent for the rest of the show by turning speech into gibberish: repeatedly throughout, people cannot express their thoughts through the crude building blocks that are words, and it is this which lends the show a melancholia that balances its daftness.

While the source material for this show is Lerner and Loewe's musical, My Fair Lady, it's fair to say that that work survives only as a set of motifs and themes, and the odd line making a knowing nod back to the original. Characters are fluid: at least three people can be said to represent aspects of the Eliza figure, and an introductory programme note makes reference to people and things never mentioned in the performance.

As perplexing as it is pleasing, Meine faire Dame does not allow easy decoding, but continues to give food for thought long after it is seen.

Lowland Hall, Royal Highland Centre, 473 2000, 17 & 18 Aug, 2pm; 19 Aug, 7.30pm, £25--£30.