Jian Liu is working up a sweat.
It's the first thing I notice as he runs through the opening of Ravel's "Piano Concerto for the Left Hand" in his office studio at the New Zealand School of Music.
Liu is performing the work with Orchestra Wellington this Saturday 28 September, and I've come down to his office to see not only what a one-handed concerto sounds like, but what it looks like.
Wiping his forehead, Liu explains the French composer's work may not be the hardest thing he's taken on, but it's certainly one of the more unusual.
For a start, why just one hand?
"It's an interesting story," Liu replies. "The pianist Paul Wittgenstein who lost his right arm in World War I commissioned Ravel to write this concerto."
The Austrian pianist asked a whole lot of the leading composers of the day to write music for him so he could continue his career, but Ravel's concerto is the one most often performed after Wittgenstein's death. A lot of people reckon it to be twice as good as most two-handed works.
Wittgenstein wasn't so sure. The brother of the philosopher Ludwig, Paul was as prickly as his sibling was difficult to understand.
He took it upon himself to make changes to the work without Ravel's permission, and complained that it was too jazzy and not classical enough.
He also took exception to the long passages where the piano plays alone.
"He told Ravel if he had wanted a whole lot of solos he would have asked for a piano sonata, not a concerto," Liu says.
However, those solos are the heart and soul of the work, like soliloquies within the wider drama of the piece where the pianist battles it out with the orchestra.
For Liu, it's not difficult to hear the echoes of war in the music. Wittgenstein lost his arm, but Ravel lost many of his friends in the war that was supposed to end all wars.
Being for the left hand, the one that plays a piano's lower notes, Ravel makes a lot of instrument's darker textures, and that carries over into his use of the orchestra.
The piece begins with the double basses, and the first instrument to join them is one of the deepest of all: the contra-bassoon, in one of the few solos anyone's ever written for it.
Other instruments emerge out of the gloom and the music builds to a climax, and only then does the piano enter - on its own, of course.
And not only does Liu have to perform alone with just one hand, but Ravel does his best to create the sound of two hands at the keyboard with just five fingers.
Liu shows me how the composer writes a part where two rhythms are running simultaneously, one in double, the other in triple time. Hard enough when you have two hands, but try dividing that up between just five fingers.
The composer does throw the soloist one life-line: there's a lot of use of the sustain pedal which allows notes to keep sounding after you've taken your hand off the keys.
I asked Liu to demonstrate a passage without the sustain pedal, and then again with the pedal as Ravel wrote it.
The first run through sounds disjointed. The second is pure music.
You could say it's a Concerto for the Left Hand and the Right Foot.
So what's Liu's right hand doing when his left is doing all the work? Does he sit on it? Tie it behind his back?
Liu prefers to let it hang loose most of the time, except when he needs it to pull his body around so his left hand can reach places at the top of the piano it normally doesn't have to go. Remember, Ravel wanted this to sound like a two-handed concerto.
And is he worried his right hand might get out of practice?
"I've noticed my left hand notes are getting a lot stronger."
Liu won't be wasting any time getting back into the normal ten-finger flow of things. His first two-handed gig after his date with Orchestra Wellington is the next day in Christchurch.
As for Wittgenstein? He eventually realised Ravel had written him a musical masterpiece and played it the way Ravel wrote it. In fact, the story of the piece even made it into popular culture when it featured on an episode of the TV series M*A*S*H.