Coloring outside the lines is a relative concept in the tyrannically ritualized world of classical music. Creativity is welcome - but please, nothing too creative. In reformatting the piano recital Wednesday night at the Kimmel Center the way he did, Jeremy Denk knew he'd better have a compelling justification.

Happily, his point in amassing a half-hour block interspersing Schubert and Janácek was something more than a concert-hall invasion of the iPod Shuffle aesthetic. Others on this Philadelphia Chamber Music Society series have manipulated presentation - a joint recital by pianist Richard Goode and soprano Sarah Schafer comes to mind. Denk wasn't making the point that Schubert influenced Janácek - Janácek sounds like exactly no one - but that perhaps each heard similar harmonic and motivic material in the air and made it his own.

You didn't need to be an ethnomusicologist to sense an Eastern European longing in both, nor a practitioner of Schenkerian analysis to hear cells in Schubert's Moments musicaux becoming different life forms in Janácek's On an Overgrown Path. Schubert's Moments musicaux No. 4 has always seemed Brahmsian in the way the right hand telegraphs harmonic progress in a series of dots and dashes. But in a Janácek context, the mind started to wander. Was Schubert - whose churchy harmonic sense and love of folk dance are well-established in the mind - invoking the cimbalom so obvious in Janácek?

The self-questioning seeped into the rest of the recital, even retroactively to the Haydn sonata with which Denk opened, the C Major, Hob. XVI (the No. 50). It starts with classic Haydn simplicity - isolated descending notes, like droplets of rain. But these develop into torrents of ideas, and pretty soon you hear where Beethoven comes from. All the way at the other end of the recital, Beethoven closed: the Piano Sonata in E Major, Opus 109. Denk was clearly challenged by the piece, especially the thicket of the third movement. But even through his sense of struggle, Denk communicated values far more important than technique: a sense of journey, especially in that last movement, which perhaps picks up Schubert's waltz from earlier, and then turns an earthbound dance into a variation that approaches the Grosse Fuge in its cosmic searching.

Denk's individuality as interpreter came forth most strongly in Beethoven and Schubert, where he re-emphasized certain lines, extending the time-release of notes in some places and contracting it elsewhere. When he chooses to shade a phrase with a particular color, he can set ablaze with emotion even an unsuspecting inner voice. But mostly, this was a recital as an act of modesty, with Denk a kind of medium. As human beings, these voices long ago fell silent. As composers, they are still speaking to each other - scarcely running out of things to say even now.