Even when the piano on the Perelman Theater stage is a sturdy Steinway concert grand, an on-site tuner is needed when the recitalist is Vladimir Feltsman. On Wednesday, the need arose first at intermission, after a pair of Haydn sonatas. Then, midway through Chopin's four ballades, more was required, though Feltsman probably wouldn't have stopped otherwise for anything less than an earthquake.

The 60-year-old Russian-born, U.S.-based pianist is not a pounder. But he plays a piano as though he is speaking through it. And he has a lot to say, which meant that the Haydn Piano Sonatas No. 34 and 49 - conversational even in the most conventional performances - have rarely seemed more eventful. And Chopin's downright confessional ballades were almost epic in scope, unfolding one trauma at a time. Like Feltsman or not (and I do), you're bound to remember his Philadelphia Chamber Music Society concert for awhile. Rarely do I spend so much time at the edge of my seat.

After some extreme years when Feltsman seemed to be in his own stormy world, rather distant from that of his audiences, his playing here felt consolidated. His inner coiled spring was less tense, bouncier. He has spent years as a Bach specialist, and that composer's rigorous logic has given his Chopin the kind of detail that reveals the music's meticulous craftsmanship. Each ballade felt like a mass of wildly dispersed notes on an inevitable path toward coherence, but one full of diversions even for listeners who think they know the way.

In the recitative-like opening of the first ballade, Feltsman organized phrases so that each seemed to have a few stray notes at its conclusion, as if the musical thoughts had no end. Though Feltsman has the fingers to keep every note in its place and the razor-sharp sonority to show you how everything could fit, he kept the music in shouting distance of chaos. Hand coordination was often a nanosecond off, giving the music's passion an extra sweatiness. In playing the four ballades as a cycle of sorts, with little pause between, the dramatic apex was the third ballade. But in yet another surprise, the devastated melancholy that begins the fourth had great surface charm, as if the music wore a party mask - though one that didn't stay on very long.

For all of Haydn's external elegance and the crystalline sonority Feltsman brought to the music, each movement seemed full of loose ends, delightfully so, in performances so elegantly layered that the mere shift in piano texture, such as the entrance of a bass figure, had a quietly seismic effect. And to think that it wasn't so long ago that Haydn's piano sonatas were considered inconsequential.

Contact music critic David Patrick Stearns at dstearns@phillynews.com.