Certain basic assumptions about music-making have changed - profoundly - since, say, the 1920s. To hear recordings of such pianists as Alfred Cortot and Vladimir de Pachmann is to perceive, in particular, a rhythmic volatility rarely suggested in our age of stamped-out, scrubbed, sterilized interpretations.

But to hear Ivan Moravec on Friday evening at the Folly Theater was to be transported, as if by sorcery, to those lost realms of musical fantasy. It was playing that seemed from another world - deliciously unpredictable, every note suffused with magic, innocent of routine or rule-book expressivity.

For all that, nothing seemed arbitrary or capricious: nothing exalted the performer at the music's expense. And even the most extravagant toyings with rhythm never left any doubt of the music's inherent pulse.

To hear the 60-something Czech pianist's Chopin was to realize what pale offerings we now accept in this composer's name. The C sharp minor Etude from Op. 25 sounded as if extemporized on the spot, but with no lack of integrity. The F sharp major Barcarolle (Op. 60) bobbed and swayed as if on water.

The A flat major Ballade (Op. 47) worked itself into tempestuous climaxes, ever balancing spontaneity and inevitability. The G minor Ballade (Op. 23) fairly ached with poignancy.

The opening of Beethoven's 32 Variations in C minor (WoO 80) was like a splash of cold water in the face - surely just what Beethoven had in mind. This may not be top-drawer Beethoven, but Moravec's sassy performance made it riveting.

In a group of Debussy Preludes, drawn from both books, Moravec made the piano the very antithesis of a percussive instrument. Notes weren't so much struck as set aglow.

Quiet as they were, the deep, bass notes of The Engulfed Cathedral could be felt through your ribcage. Wonderfully misty sounds shrouded the aptly entitled Sounds and Perfumes Turn in the Evening Air. Fireworks flashed, fizzed and boomed, but as from an unearthly remove. Moravec didn't so much paint pictures as animate dreams and fantasies.

This was playing of astonishing color and nuance - and, where called for, virtuosity. But so wondrous was the music-making that mere means attracted no attention. The magic continued through three encores: a Chopin A minor Mazurka, a B minor Capriccio by Brahms and a Smetana Polka.

No doubt about it: Moravec is one of the artistic treasures of our age. Any chance the Friends of Chamber Music - presenter of this recital - might make him an annual visitor?

And if he does return, don't even think about missing it.