Lang Lang, Royal Festival Hall

There must be at least 100 more interesting pianists in the concert world than Lang Lang, but perhaps he is just the best publicist around, because nothing else can explain why such a vacuous display as he gave last night at the Royal Festival Hall could bring a standing ovation. Most of the evening felt like being on a plushly cushioned chintz sofa with Tinkerbell, listening to Bach, Schubert and Chopin being served as a cream tea. Lang Lang Inspires is the slogan at the Southbank Centre all this week, but what is inspiring? His art - or just his vast skills as a public communicator, with 40 million Chinese piano students now credited to the Lang Lang effect?

After roughly 30 seconds of his opening for the Bach first partita, I felt a sense of doom. This would be a two-hour session with a man with whom I feared I was unlikely to have more than a moment’s interesting contact - though I'd be wrong at least for two minutes (of which more later).

This is what happens at a piano recital, or indeed with any recital: burdened by the memories you carry about with you, the tracks and expectations that certain master musicians have cut into your soul, you come sensitised to the music already, raw in certain ways - and then in comes this showman with his precious, kittenish phrasing and facial expressions like a St Sebastian yearning for more and sharper arrows to come pierce his body. And you sit there aghast through the ingratiating, tutti-frutti Bach, thinking: "And he’s going to do the Schubert B flat sonata now. Cripes."

And cripes it is. Lang Lang, 28, is the new generation’s Liberace. Not content with simply overcolouring, oversweetening every phrase, almost Photoshopping the playing - dragging, smearing, blurring, enhancing every highlight and accent - he mugs distractingly to the gallery and you quickly have to decide whether you can bear to watch. Cameras really should be zooming in on every facial wince as he weights a silky chord, or on the saintly smile he bestows on the audience as he flourishes away a difficult arpeggio with pin precision.

He began the great, enigmatic, effortful opening phrase of Schubert's last piano sonata with the ease and lubriciousness of a sultan sinking into silk pillows humming a serenade to a hidden lovely. It was arresting - you seldom hear this opening played with such a seductive balminess (or with such ecstatic yields of the head backwards with eyes closed). But this work exposes that Lang Lang has only one answer to the pp instruction, which is the most veiled, delicate, sugary sound - not for him the unnerving possibilities of pianissimo, the gradations that can chill the blood or open up layers of distant memory.

And the other is that the challenge of long-distance playing eludes him. Worthy performances of this piece have a long-range weather system to them, a grasp of underlying inexorable currents as well as temporary gusts, of how nothing is ever the same, even the repeats. Those returns of the first movement’s main theme - on which other much finer pianists can somehow suggest peeling off successive layers of time and association - for Lang Lang seemed to be what he was looking forward to most through the passages of change, to bathe us all in his salon-pianist sunshine.

This shortage of insight and imaginative fantasy made the three other movements wearing in their elfin affectedness. And the electrical flash-storm of the finishing bars came over as the purest calculated effect, to whip the audience to shouts, whistles and catcalls, and the flashes of dozens of phones taking pictures of him.

By this stage, all I was expecting from his interpretation of Chopin’s Op 25 Études (Studies) was a flawless surface. Mostly that was true. The third became a kind of brash, sophisticated strumming, rather than an invigorating series of splashes. The fifth, marked Vivace and usually an enjoyably jagged ride through barbed spread chords, was smooth and treacly, to enable maximum syrup to be extracted from the Più lento big tune.

Some exquisitely, almost inhumanly rapid double trills in No 6 heralded an arrestingly long pause in which Lang Lang contemplated the heavens and communicated with gods while the audience held its breath. Five more studies went by, predictably saccharine, or bouncy, or oompah under the phenomenally swift and flawless fingerwork, so much so that one was practically tapping one’s foot.

And then, suddenly, the 12th étude. While the 11th had had all the characteristic barnstorming and Technicolor excess, Lang Lang segued into a most unexpectedly rigorous last - and for two minutes I was totally upended. Here, suddenly, was a little boy who’d practised hour upon hour against the metronome, sweeping those huge arpeggios up and down the piano without cease, compelled by some uncomprehending need to repeat and repeat - yet it was the one study of the set that is most clearly a pianist’s athletic workout. The furious technical challenge in which he found liberation for his soul pierced my heart. Deep, very deep down inside Lang Lang there could be a sincere and humble musician - but is it a priority for him, amid all this adulation? Lang Lang admirers would learn plenty by just getting out to, say, Mitsuko Uchida, Murray Perahia, or even the younger Simon Trpceski, to hear how pianism and soul ally.

• Lang Lang plays again at the Southbank Centre this week, in a trio with Vadim Repin and Mischa Maisky tomorrow, in a concerto concert on Saturday, and in a "Massed Piano Concert" on Sunday
• Lang Lang's website

Watch Liberace play "The 12th Street Rag" - listen for the double time section