Of course it's a calumny on the real Roger II, who was known in 12th-century Sicily as al-Mu'tazz-bi-llah, the Baptised Sultan, on the strength of his multicultural capacity to live and work with Arabs, Greeks, Byzantines, his own Normans and, I suppose, the native Sicilians. Indeed, Roger's Christianity only went so far as to commission a mosaic showing himself being crowned by Christ. But, despite Szymanowski's two happy visits to the island before the First World War and his commentary after the disasters of that war and the Russian Revolution: “If Italy did not exist, I could not exist either. Italy – the homeland of all dreamers about a heightened sense of living – rose within my inner vision in all her imperious beauty and seductive grace”, his opera set around the King was more about his own repressed sexuality than either the island's history or the colourful monarch.

Which is why director Kasper Holten has set this Royal Opera House/ Opera Australia/ Dallas Opera co-production in the King's head – literally. The eight-metre tall construction, even more dominant on the tiny Sydney Opera House stage than at Covent Garden in 2015, comes to life brilliantly under Jon Clark's kinetic lighting and, when it revolves in Act 2, represents the three Freudian levels of the subconscious: superego (an observatory), ego (the King's library) and id (writhing, naked male dancers).

Does an opera audience appreciate this level of concept? In Sydney, I suspect the action involving the surprisingly active Nietzschean battle between Roger's buttoned-up dedication to the rationalism of Apollo and the mysterious Shepherd's smiling offers of Dionysian dance and freedom of thought took most of our attention. From the start, Michael Honeyman's Roger has been as tight as a drum, and one can imagine how tempting his wife Roxana might have found it to 'go over' to the looser and cooler Shepherd. He's played by the only survivor from London, Saimir Pirgu, elegantly clad in an orange Indian coat to match Szymanowski's efforts to achieve “perfumed, oriental melodies of an exquisite, haunting beauty”. All around him are in the greyest of 1920s serge.

Sadly, the crowd keeps to grey even after it's danced off following the Shepherd; even sadder, Roxana, having caused Roger's collapse with a wild dance accompanied by a hail of books from the library, fails to dance off with them, but quietly disappears aboard the turning head.

Fortunately, Lorina Gore's queen had left a strong impression with her famous aria – seeking to unstiffen her spouse in a language as coloured as the Shepherd's, referring to “serpents are coiled asleep on beds of lilies”, and “even the leopard tires of blood”. She does it strangely and movingly. But it takes her departure to move Roger and his distinctly un-Arabic vizier, Edrisi (Idris in real life) sung with bureaucratic calm by James Egglestone, to follow the crowd. And this despite its suspiciously Nazi burning of Roger's books in the fiery remains of that Freudian head. I've never thought of Hitler and Dionysus in the same bracket before!

Does the now-barefoot and shirtless King find a balance in his mind as the smirking, now-darkly suited Shepherd/ Dionysus leaves the scene? The synopsis suggests that he does. This production, well revived by Amy Lane, left me wondering; but the amazing sound world developed by Szymanowski over his seven years writing King Roger in which not a single individual instrument broke through a seamless wall of orchestral sensation may have distracted me. I was also blinded by the sunlight, in which Michael Honeyman was bathed as he sang in words reminiscent of Prospero's: “And from the deep of solitude, where drowned my power lies, I'll tear my crystal heart as an offering for the Sun!”. A powerful change of heart? But wasn't his buttoned-up Apollo also the sun god?

I guess it's the libretto's equivocation that has denied King Roger the frequency of performance that its music – developed over those seven years from its opening Byzantine hymn, via a not-wholly convincing orientalism to a unique orchestral voice – deserves. It was only introduced to London in 1975 by Aussie Charles Mackerras, and has only been seen in Australia in the innovative hands of choreographer Graeme Murphy, who found the terpsichorean element of the Shepherd's 'new' religion just right for his Sydney Dance Company in 1990. Like Szymanowski, whom Murphy frequently used for his dances, he had spent an inspiring sabbatical period in Sicily.