Mark-Anthony Turnage’s opera Festen was too big to fail, and in many ways it didn’t. A luxury cast with considerable strength in depth excelled through 90 minutes of relentlessly bleak action. That a brand new opera felt the right length for its subject – and could have even been slightly longer – was a rarer thing still. There was even a laugh out loud moment, as tenor Allan Clayton burst through a door, Big Bird style. If only the music had been better.

Turnage’s sour, spiky style is established enough to have its own stock language of gestures. (His way of setting swearing – short and exclaimed – becomes almost meta in Festen.) But, following his operas Anna Nicole and Coraline – two stories which lent themselves extremely well both to musical and specifically operatic expression – a leap of compositional logic was required to tackle Thomas Vinterberg’s cult Dogme 95 film Festen, a foundational film of an avant garde movement that forbade the use of non-diegetic music. And, rather than facing down the impossible – how to align the Dogme aesthetic of spartan purity with his own, of coarse excess – Turnage dodged the question and wrote the music to a different opera entirely.

Turnage enjoys fusing something called jazz with something called classical. After growing up around Essex’s soul-funk scene in the 1970s and 80s, fusion has bubbled through his music since his breakthrough opera Greek, spurting out in works like Blood On The Floor, his first foray into improvisation, or Scorched, a “re-composition” of material by guitarist John Scofield, for orchestra, big band and trio.

In the buzz around Festen, the watchword was not jazz, but its distant relative, jazzy. Festen “is quite jazzy in places”, he told The Times, ahead of the run of performances earlier this year. (“I hope it’s not bland, but I don’t think the music will offend anybody even if the subject is difficult,” he added.) Turnage went one further when introducing his recent guitar concerto Sco (another piece that involved Schofield) as part of a marketing package for London Symphony Orchestra: “All my pieces are pretty jazzy,” he said.

What does it mean to be jazzy, exactly? On a fundamental level, jazzy implies something being held at arm’s length. To be jazzy is to not be jazz, but, rather, be like jazz, and, crucially, be distant from jazz. It’s used in conjunction with other distancing language. Something jazzy is only ever partially so; music can be a bit jazzy, jazzy in parts, quite jazzy, pretty jazzy, or contain jazzy bits, but it can never be extremely jazzy, fully jazzy, or even jazzy full stop.

In Festen, inverted commas “jazz” became one patch on a larger quilt of pastiches. Turnage has form in this. In Anna Nicole, he seemed determined to write in an old-fashioned way, with bossa novas, waltzes and other dance forms treated as stock in a sub-Sondheim manner, with added Turnage pep; this trend continued in Festen, with its weird conga and racist nursery rhyme. The figures he used were exactly the sort of cliched gestures you might expect to appear if the composer had pushed a button marked “a bit more jazzy”: swampy brass, bluesy inflections, Gershwinny orchestrations, opulence, vulgarity and raucousness, all dialled up. The effect was not specifically anachronistic – a precisely treated pastiche of a moment in time could make for an interesting narrative jolt – but instead doused the whole piece in Old. Much like in Anna Nicole, Turnage wrote old fashioned music here – not from a time, but suspended in a time long ago.

The jazzy thing is a British thing, and, I reckon, a male thing, a relic from the age of the multi-talented TV showman. Roy Castle was a jazzy man, as was Bruce Forsyth. Richard Stilgoe, as Peter Capaldi’s Thick Of It character reminded us, was “a jazzy bastard”. Jools Holland, with his ubiquitous boogie-woogie and interminable chat show rambling, is today’s exemplar jazzy man.

For the younger generation, Jacob Collier is the digital version of the jazzy archetype. (A different aesthetic taxonomy is attached to jazziness; virtuosity and aptitude are elevated above anything more spiritually, philosophically, emotionally, or sonically probing.) With its own distinct set of musical signifiers, a way of ranking good to less good, and a dedicated audience, jazzy is less an adjective than a genre in itself. And depending on how brave you’re feeling, you could probably argue that Robbie Williams (of Swing When You’re Winning and Swings Both Ways fame), Bradley Walsh off ITV quiz show The Chase, and even journeyman Football League striker turned Sky Sports broadcaster turned big band crooner Chris Kamara could all be included within this jazzy bracket.

It feels a little unfair to dunk on this insincere, nakedly commercial, soulless, fogeyish, rather male genre of music. Set within its self-defined boundaries, it works, and people find joy in it. My own musical education came via the true protectors of the jazzy flame: brass bands. Yet you know exactly what the sudden entrance of jazzy music sounds like: overly deliberate swing; tsk-tsking cymbals played by a drum kit struggling to sound surreptitious; a sudden, overwhelming feeling of noteyness; a handbrake turn from seriousness into frivolity; and the awkward introduction of embodied concepts like feel and groove into spaces which have traditionally expelled them. A recent London Cafe Oto gig was the first in a while I had to walk out of. Following new works by Laurence Crane and Cassandra Miller was an arrangement of Schoenberg in a dance band jazz style that contained all of these jazzy trappings.

The jazzy continuum is one among many narratives of jazz in the UK; many better ones exist. But in a country with little institutional infrastructure to uphold a popular jazz narrative – even if its only purpose is for others to rail against it – we rely on musical representation as a way of telling and retelling the story of what this is and why it matters. One of those that concert halls rely increasingly on is that delivered by Wynton Marsalis, to whom the UK classical industry turns when it wishes a straightforward (read: reductive) version of what jazz is. Another narrative is this jazzy one, which neglects the long, rich, endlessly developing and ultimately unbottleable artform in favour of a set of signifiers; a cluster of cliches rather than a careful, curious engagement with where the form might be today. And in the process of jazz becoming jazzy, it also becomes trapped in its own weird register: a continuous past tense, where music is simultaneously timeless and old.

Jazzy music will be just fine. Others should be wary of a descent into simulation.

Hugh Morris is editor of VAN magazine.

This essay appears in The Wire 495. Pick up a copy of the magazine in our online shop. Wire subscribers can also read the essay in our online magazine library.