The Giacomo Variations takes its time really getting down to business – the business Giacomo Casanova was in – the business of love.

It begins with a lot of theatre business. The set, designed by Renate Martin and Andreas Donhauser, consists of three gigantic Marie-Antoinette skirts. Lift one and there’s a bed for romping. Part the pleat of the stage-left skirt, and there’s Giacomo’s study, where he writes his memoirs and receives his leading-lady publisher, with whom he reminisces about his life and loves. The slit of the stage-right skirt opens like a womb and out of it issue characters (played by real singers) from the business of Mozart operas – Così fan tutte, Don Giovanni, and Le nozze di Figaro.

When John Malkovich first takes the stage as Giacomo, the audience spontaneously applauded – and you thought the evening was about being John Malkovich. But Malkovich slipped into being Giacomo, moaning “I want a woman”. He copulates with a chambermaid, and being old, collapses into a heart attack, twitching and spasming, so you don’t know what to think. And you don’t know what to think as the Orchester Weiner Academy, led by Martin Haselböck, strikes up “Eccovi il medico” from Così fan tutte, and paramedics appear to load Malkovich onto a collapsible gurney, and the maid shows up with a pair of (unplugged) magnetic paddles “made by Dr Mesmer”, and shocks him back to life.

Then there’s more muddle of theatre business, as director Michael Sturminger’s scripted mix of Casanova’s Memoirs and Da Ponte’s libretti develops. From the slit in the third skirt come Figaro and the Contessa, and from under her skirt crawls Cherubino, who sings “Non so più”. He/she merges with a girl Giacomo remembers, who embraced him disguised as a castrato, uncovers man parts for Giacomo and the audience, then discretely pulls them off and drops them onto the stage. It takes a lot of Malkovich and much more Mozart before the various businesses coalesce and come to a common point, but they do, and it’s this: Giacomo Casanova’s life was ruled by love. All the variations on his multiple amours, which appear to include incest, rape, and marriage, were inspired by love that lived, died, and was continually resurrected in him. By the time Casanova’s connection to love and death soaks in, half-way through the first act, all the businesses of the production join to produce a steady stream of meaningful pleasure.

Malkovich is convincing, even when he sings, solo or with the real singers in the cast who bring to momentary life Mozart’s Donna Elvira, Susanna, Despina and Zerlina. Lithuanian co-star Ingeborga Dapkūnaitė has a mysterious delicacy in her voice. She radiates a mature, amused sensuality as the publisher Elisa I, that blends well with the lovely and funny and youthful Elisa II we got from Kirsten Blaise. Daniel Schmutzhard brought his sturdy baritone to the role of the young Giacomo, as well as Figaro, Leporello, Count Almaviva and Don Alfonso.

The Giacomo Variations is an eccentric hybrid of 18th-century erotica, Hollywood Californication, and star power, with Mozart’s greatest hits. That is a lot to swallow. What makes it go down is Malkovich’s sincerity: being Giacomo and simultaneously being himself. This chamber-opera-play also gets a great assist from the parts in the libretto which make room for Giacomo to honour his anger – his willingness to put his life on the line in defense of the way he experienced love.