He may have been responsible for Bayreuth’s staging of Tristan und Isolde, but the Swiss director Christoph Marthaler’s UK debut is with a quite different show. King Size, brought to the Royal Opera’s studio theatre by Theater Basel, is his riff on the idea of a Liederabend, an evening of song.

In a hotel room are four characters: a singer-pianist, a couple and a well-turned-out old lady who haunts their dreams, speaking but not singing. If it is indeed their dreams we are seeing. People disappear into cupboards, change costumes and wriggle from under the bed while singing about love in a medley that gives equal weight to songs by Alban Berg, John Dowland, the Kinks and the French pop singer Michel Polnareff. No one has an operatic voice, and at least one isn’t even an especially good singer, but that’s not the point.

There’s no interval, which is a shame because it’s the kind of show that cries out for a drink; perhaps a hip flask would help, if only to dull the discomfort felt on the way home when you realise that it is not any of the Schumann songs or even the sweet German folksong at the end that is stuck in your brain, but Keeping the Dream Alive by Münchener Freiheit.

The humour is absurd – if you’ve ever wanted to see a granny eat spaghetti from a handbag while an offstage trio sings the Perdono passage from The Marriage of Figaro, this is your show. Some of it works: it turns out that the prelude to Tristan und Isolde, with all its frustrated yearning, is the perfect soundtrack to someone trying and failing to open up a music stand. Some jokes don’t travel so well across the Channel. I’m not convinced King Size adds up to as much as it thinks it does, but somewhere here there is something to make anyone smile.

• At Linbury Studio, London, until 18 April. Box office: 020-7304 4000.