If a night at the orchestra were a pure investment-return transaction, Lang Lang certainly gave Thursday's audience its money's worth. It's when the actual music entered the equation that things got a little dicey.

You had to look past a lot to hear it. At the front of Verizon Hall stage, with Simon Rattle leading the Philadelphia Orchestra, the pianist air-conducted or air-trilled with an idle hand when Beethoven failed to give him enough to do, mugged all manner of facial expressions, and kept leaning out to look at the audience, as if to ask: Do you like this? They did. I don't think I've ever heard a spontaneous audience roar quite like the one that greeted the encore. Lang Lang and Rattle did Dvorak's Slavonic Dance, Opus 46, No. 1 seated together at the keyboard, piano four-hand. Rattle joked that he had decided to keep his day job, but he was being modest. They gilded the piece with great lift and animation. This act might have legs.

Let me just take the pledge right up high: I fully support Lang Lang's right to be Lang Lang. What a wonderful thing it is that this personality, for which Philadelphia bears partial responsibility (he is a Curtis Institute graduate), is as individualistic as it is. I also respect the non-believers in the audience — of whom there were at least a few — who prefer their Beethoven less addled. The Piano Concerto No. 3 in C Minor was subject to arbitrary accents in the first movement, jarringly extreme dynamics in the third, and an exquisite portrayal of serenity in the second. Rattle's trademark observation of very quiet pianissimos set a mood that went unviolated in that section. He kept the strings lean and the textures permeable, which allowed Lang Lang's tone to ring. A little farther out on the spectrum, the pianist recalls violinist Anne-Sophie Mutter, whose transgressions of taste in some places come in a package that also brings frightfully human insights. Lang Lang's exploits are more arbitrary (why the third-movement violence?), and yet his presence in the hierarchy of top soloists remains felicitous.

Rattle always remakes the orchestra during his visits, righting indulgences and generally restoring the ensemble sound to its most homogeneous state. Nimble, too. He used Unstuck, a 10-minute score from 2008 by California-raised Brooklyn composer Andrew Norman, as a curtain-raiser, the cartoon before the feature film. It has, in fact, something of a cartoon in it, a series of flickering references to Bernstein, John Adams and others that last just seconds, as if he were channeling Carl Stalling's Looney Tunes. Extremely skilled, this piece. It also raises the question of where technique ends and a genuinely original artistic statement begins. There's enough there to impel further inquiry.

Rattle's second half was a seamless elision of Sibelius' sixth and seventh symphonies. It turns out that the seldom-heard No. 6, with its pastoral openness and movements that end inconclusively, leads right into the majesty of No. 7. The pacing echoed Karajan's, sustaining rock-against-hard-place tensions, but not at the end, where Rattle sensed what kind of impact quick resolution can have when wisely gauged.