The Importance of Being Earnest, Barbican Hall

Gerald Barry's new operatic adaptation of Wilde's The Importance of Being Earnest delivers a number of firsts. The first opera score to contain an ostinato for smashed plates. The first orchestra to include a part for pistols and wellington boots. The first opera (that I know of) to offer the role of an aging mother to a male bass. And the first opera I've been to where I've cried with laughter.

Granted: on paper it all sounds a bit Chuckle Brothers. Smashing plates, wellies, travesty roles aren't automatically funny at all. But like all the best jokes, these are not jokes. Barry doesn't resort to the plate-smashing etc in order in the first place to make us laugh. He resorts to them in order to get to the truth. And the truth is that the aural metaphor best suited to the famous catfight between the prim belles Gwendolen (the dead pan Katalin Karolyi) and Cecily (the dazzling Barbara Hannigan) in which they find out (or rather, fear they've found out) that they're both betrothed to the same man is undoubtedly the syncopated smashing of plates. This is the sound that gets quickest to the psychological nub of the matter. And Barry follows the action through to the very end of the girls' two-way. Deadpan. Convinced of its own seriousness. 

Different sections of the orchestra burst out at us like spitting pimples

Barry's work also improves Wilde's play. A grand claim, possibly, considering many think Wilde's Earnest to be one of the most perfect plays ever written. But for those, like me, who are allergic to Wilde's wit, this is the perfect antidote to and improvement on the urtext. The vocal music (full of the usual Barry acrobatics) destroys the pert one-liners. It tears up the neat little lawns of wit that Wilde has anally manicured. And in its place Barry lays down a proper comedy: one that is wild (and no longer Wilde), modern, genuinely funny and true.

And that last point is the most important. Truth, honesty, upfrontness, earnestness is famously the thing that is missing in Wilde's Earnest. This is what Barry's music fills in. The psychological truth. And it's not pleasant listening. The small chamber orchestra - the superb Birmingham Contemporary Music Group under the energetic watch of Thomas Adès - became a heaving, grunting mass of repressed rage at this Barbican European premiere. Different sections burst out at us like spitting pimples. The fortissimo flutter-tonguing horns for the entry of Hannigan's Cecily was one of many memorable orchestral eruptions.

The anger even starts to engulf the musical tradition. Several chunks of Beethoven's Ninth are spat out in a disfigured form. "Auld Lang Syne" is heard on flute struggling against dense orchestral figures. Several other musical bits and bobs are tossed out at us.  Chabrier-like quotations on the trumpets. A Paisiello-like French Revolutionary march. A G&S pastiche. Even a quote from his own opera The Bitter Tears of Petra von Kant. All of it is refracted through Barry's hard-edged musical voice: one of the most punchily attractive there is.

Lady Bracknell is made to sound like a Nazi madman The welter of activity is a foil to the cool, calm polish of Wilde's words that creates a kind of schizophrenia: the music doing one thing, the characters another. Thoughts on muffins or Victoria Station are fire-crackered across the singer's vocal spectrum. Peter Tantsits's John Worthing and Joshua Bloom's Algernon Moncrieff deserve special praise for expertly traversing above and beyond their natural range.

For Barry every line no matter how trivial has an emotional reservoir running under it. In this he's taking the lead from Wilde who, when asked what the theme of Earnest was, said, "That we should treat all trivial things in life very seriously, and all serious things of life with a sincere and studied triviality." In this way, the seemingly innocent admiration of Cecily's physical features by Lady Bracknell (the fabulous Alan Ewing) is pounced upon and made to sound like the ravings of a Nazi madman. In the process, we get something not jolly or surreal but unnervingly laugh-out-loud.

The key is Barry's counterintuitive streak. Few other composers would think that the words of Wilde would speak more sharply if one went against their natural rhythms, that one would amplify the humour of the whole by ignoring the careful humour of the specific, that one could be so brash and unpolished with something so delicate and polished. Most other living opera composers seem to be interested in trying to see how words can fit with music, how the music can fit with the plot. For them, it's about homogeny and echo and unified neatness. For Barry, it's about the words and music - about what we say and what we feel - being at war. The result is two hours of unimpeachable brilliance.

• Catch Gerald Barry's Importance of Being Earnest in Birmingham on Saturday, 28 April