When András Schiff begins his survey of the complete Beethoven piano sonatas at Carnegie Hall this October, it will represent nothing short of a pianistic mountaineering expedition for this ever-popular Hungarian musician. He has performed the cycle in Europe, but even if the prospect is less daunting than it was the first time, the process doesn't necessarily get easier. "It's no small undertaking," agrees Schiff. "It really is like climbing the Himalayas again and again. It doesn't mean you know the secrets of the Himalayas, but at least you climbed them! So now I am off to some further explorations." He is presenting the concerts over two seasons at Carnegie Hall, including four concerts this season.

Schiff, deeply serious yet with a wry, twinkling sense of humor, and his wife, the Japanese violinist Yuuko Shiokawa, divide their time between London and their home in Italy. On a table in the Italian home lies the latest acquisition in his collection of Russian icons: the image is exquisite, delicate yet strong, austere yet perfectly drawn, and it possesses a sense of mystical concentration — not unlike Schiff's playing. He is something of a music collector too, having long been associated with complete cycles of works, including Bach's Well-Tempered Clavier and Schubert's sonatas, among others. Yet Beethoven, he says, remains "the ultimate challenge."

He will open the cycle at the best place to start: the beginning. "I still believe, as I always have, that the Beethoven sonatas should be performed in chronological order," he explains. "I wouldn't like to play them in a mixed order, as many other pianists do, because I feel it's a logical journey that shows a sense of evolution. Beethoven, from the first sonata onward, never repeats himself. Perhaps Shakespeare is the only artist with a comparable variety. For instance, Beethoven often puts three sonatas of completely different character together under one opus number. One might be dramatic, the second lyrical, the third comical — so one opus encompasses three different genres."

The early opuses — too often underrated beside the celebrated middle-period works like the "Appassionata" and the questing, deeply personal last sonatas — contain some of the most magical examples of this. "I love Op. 10, No. 3: it's an absolute masterpiece, and very mysterious," Schiff says. "There are certain pieces that you can characterize easily — the first sonata, Op. 2, No. 1, is dark and dramatic, and Op. 7 is very lyrical, with an extraordinary slow movement. But Op. 10, No. 3, is totally elusive."

Schiff deliberately waited until he turned 50 before tackling the cycle; he once suggested that it had taken him this long to create the right type of sound for Beethoven. "On the one hand, there's no such thing as 'a Beethoven sound,' because the music is so varied; I had to find a different sound for each movement of each sonata," he comments. "On the other hand, there is something like a Beethoven sound in terms of density — denser than, for instance, a Mozartean sound." Playing the cycle, and developing his sound to suit the sonatas, have also affected his approach to other repertoire: "I recently went back to some Schubert sonatas that I hadn't touched for years, and I think the way I play them has really changed through the Beethoven experience, very much for the better. Something is subtly different in the subconscious. I can still scale down or lighten the sound, and it's a good thing to have the ability, or at least the confidence, to do this."

So Schiff is ready to begin climbing this pianistic Everest once again. And as with mountain ranges, there is always something new to notice in the panorama from the summit. How lucky New Yorkers are to catch a glimpse from these heights!

Jessica Duchen is a novelist and music journalist based in London. She writes regularly for The Independent and her latest book, Alicia's Gift, was published this year by Hodder & Stoughton.