For a Parisian, the accordion is the musical instrument most redolent of memories and dreams. So for Bohuslav Martinů's surrealist opera Julietta, written in Paris and infused with a discombobulating jumble of memories and dreams, Antony McDonald's sets were masterpieces: in each of three acts, the stage is dominated by a giant accordion which is more or less the size of the whole stage. Each is in a different orientation: in Act I, an upright accordion serves as a building; in Act II, the singers walk on the buttons while the bellows and keys serve as the framework for the whole stage; in Act III, the singers walk and sit on the piano keys as the bellows is turned into a giant, official filing cabinet.

The premise of Julietta is that Michel, a Parisian bookseller, is haunted by the memory of Julietta, a girl he once met on a seaside holiday. As he searches for her in his dreams, he meets a succession of characters from the town who behave in increasingly bizarre ways, mainly driven by the fact that they have no memory and can exist only in the present moment. Michel is made mayor of the town, he murders Julietta, he appeases the baying crowd by telling them a story, only to be attacked again, not because of the murder, but because the story wasn't very good.

Richard Jones's production, originally from the Opéra de Paris and the Grand Théâtre de Genève, is visually stunning, well directed on the stage, and generally makes the most of an opera that is quirky to the point where it's really quite difficult to get to grips with. The music is lovely, written in a style that owes more to the Impressionism of Martinů's adopted home of Paris than to his native Bohemia. But in the first act, it's extremely episodic: here a snatch of melody, there a brief chord progression, elsewhere a dash of orchestral colour. There's much to enjoy, but it's very hard to make it all hang together. Martinů's own synopsis, reprinted by ENO in the programme notes, doesn't do much to help, with sentences like He begins to lose himself in the world which exists only in the present, and where situations follow each other without cause or consequence.

But although I struggled with Act I, I have to admit that it's evocative of the confused nature of dreams, and as Act II unfolded, I started to really enjoy myself. As Michel awaits Julietta in the wood where they are to meet, there is a spellbinding passage in which a waiter serves up wine and memories to an elderly couple - as dementia approaches, he is the real source of the shared memories that they treasure. It seemed especially poignant to me, bringing the imagined context of the world without memories together with the complex reality of how our memories are made and preserved. When Julietta arrives, the love music is ravishing but the emotions ambiguous as Julietta finds Michel's strong grip on reality to be really quite tedious, teasing him about being like an old crocodile to the point where he shoots his pistol into the air to frighten her – or murders her, we're not sure.

In Acts II and III, my ears began to pick up a level of musical coherence that I had failed to gain earlier, and the undoubted originality and inventiveness of the score began to serve a purpose rather than simply dragging me in confusingly different directions. And I loved the premise of Act III: Michel is in “The Central Office of Dreams”, in which a kindly but officious bureaucrat dispenses dreams to those who request them (or refuses to do so, based on a variety of obscure criteria) with the door to the land of dreams depicted as a giant register switch on the accordion. Martinů's fellow Czech Kafka would have loved it.

Julietta is a long way from bel canto: the vocal lines are short and there's hardly anything for singers to get their teeth into to display their prowess to the audience. And one main role dwarfs the others: Michel is on stage for just about the whole opera. Peter Hoare gave an excellent performance, keeping up the pace and enthusiasm both vocally and in his acting. Within the limits of the title role (which, contrary to what you might expect, is not all that large), Julia Sporsén was interesting to listen to and acted well. The many other roles are mostly doubled up, with each singer taking on a variety of parts; Henry Waddington stood out from the crowd both as the Wine Waiter and the enigmatic “Man at Window”, with a memorably rich bass/baritone voice.

Surrealist opera isn't exactly an established genre, and the extreme levels of quirkiness of Julietta, together with its relative lack of music that you can latch onto and remember, mean that it will probably remain an obscurity. But once I'd settled in, it made for an entertaining evening's opera that was certainly different and punctuated by many ravishing passages of music. And this production is worth seeing purely for Jones and McDonald's quite marvellous setting.