Toby Young greets me with a smile and slams down two heavy-bottomed tumblers of gin on the table. We’re in the Groucho, where G+T’s are served with translucent slivers of cucumber and ice that looks like it has been chipped off the finest glacier on the planet; precious and chunky bobbing amongst the fizz. “These drinks could be straight out of Mad Men!” Toby says incredulously, as he dissolves dreamily into the velvet berry-coloured sofas, his face carpeted in three-day-old stubble. He’s either completely relaxed or exhausted –and with his jet-set lifestyle, I would take a stab at the latter.

After winning the Guardian’s BBC PROMS Young Composer of the Year in 2006, he has been described by his peers as having “a ready appeal which defies stylistic pigeonholing”. At only 23 years of age, Toby has composed for the London Symphony Orchestra and the Royal Philharmonic, as well as co-writing albums for the likes of Rhianna and Chase and Status: it is no wonder that both of Toby’s parents were musicians themselves. Taking a chug of his drink, he adds: “We had two pianos at home. One was a pristine baby grand, the other, a battered old upright in the corner. Possibly to mimic my dad, I one day sat down at the battered upright and tried to make up a tune. Apparently, it wasn’t that awful!”

When Toby was seven he started performing as a boy treble for the English National Opera. The one memory that has stuck with him was standing backstage in just his underwear as two make-up artists painted him white and strapped some angel wings on his back, before sending him onstage to do the ‘cherub song’. “I think nowadays we would call this child abuse.” Toby laughs, one of his dark eyebrows rising up in an arch, like a wiggling cat on a Bond villain’s lap.

When composing a piece, Toby generally adopts the Brahms model, where he starts with a little nugget of an idea and then stretches it out over a longer space using an array of compositional tools and tricks. “I always walk around with some manuscript paper in my bag, and jot down individual gestures or harmonies and melodies when they come to me, which I’ll later use as the starting points for bigger pieces.”

He rifles through his leather satchel and produces a manuscript notebook, with spidery musical notes hopping up and down five thick lines in faint graphite pencil. How strange that such humble marks will eventually transmogrify into grand emotions when played to a dimly lit audience on the string of a cello: a quaver becomes a quivering tear, a treble clef causing hearts to soar. “My background is really as a jazz pianist, and so it is always tempting to turn to the piano and improvise, but I generally avoid this if I can, as far too often my hands fall into familiar melodic shapes and chords, which stops me really thinking about what I want to say with each piece.”

And Toby seems to communicate very different things in his music. His first opera was about a terrorist, the second involved the entire cast and audience walking through a museum at night, and his last opera was set in an S&M dungeon. The dramatic form must bring out his crazy, licentious side.

But what non-musical influences have affected his music the most? “I like art that plays with our perceptions of reality or processes, so writers like Kafka or Samuel Beckett. I am also a huge fan of Harold Pinter – the way his work sits uncomfortably between tragedy and comedy is sheer genius.” Toby’s musical philosophy is to have a diverse taste in music. “I want to be able to represent this variety of sound without becoming a ‘crossover composer’. I find it shocking that people still think in such broad brush-stroke genres as ‘classical’ and ‘pop’ for music.”

One of the most crucial things for Toby when writing a new piece is that the audience can engage with it – and he doesn’t mean dumbing it down or tailoring it to be easily listened to. “I mean that it creates some sort of narrative, whether that be abstract or more pictorial, and that my gestures are vibrant and enticing. I want to be able to take my audiences on a journey, so they leave feeling an emotional connection with the music, whether it is an uplifting one or something more solemn. There is, I think, a preconception that ‘difficult’ modern music negates the audience. I don’t think this has to be the case, provided the composer knows what effect it will have on their listeners.”

Toby orders in another round, summoning the waiter with the exact hand-movements of an orchestral composer. The fancy libations arrive in all their cut-glass glory, making me wonder if these aren’t really difficult times for young composers at all. It is more likely that Toby is one of the lucky few whose diary is cluttered with projects, meaning he can afford drinks with prices that have zeros rolling off the menu at private member’s bars. “I think any time is hard for younger artists who have not yet found their voice, particularly now with horrific pressures for creative organisations to show their economic viability and worth.”

It was nearly time to call time on this tunefultêteàtête with Toby. The pop-art portrait of Che Guevara above our heads seemed to be sick of looking at us, having being so used to ogling at sun-kissed celebrity skin, not the torn, scruffy sheepskin coat of this City Uni journalist. The one question that I was dying to ask Toby before we departed was: What was it like working with Rihanna? Did she strip naked in the studio? Was she rolling spliffs between choruses? “Put it this way, she took over four hours to record three bars.” That was all I needed to know, and with that revelation, I left the joint. (Not Rihanna’s of course, the establishment).