The hipsters - some of them - couldn't take it.

Listeners departing before the end of a complete performance of John Cage's Sonatas and Interludes on Sunday at the Philadelphia Museum of Art - presented in the same building as the Dancing Around the Bride exhibition that inspired the current Cage: Beyond Silence festival - were mostly under 30 and perhaps didn't realize that Cage was being revealed as never before.

To the unprepared ear, Cage's Sonatas and Interludes, 16 sonatas and four interludes written between 1946 and 1948, might seem like an odd thicket of unconventional piano sounds. Cage specialist Margaret Leng Tan sat at what appeared to be a typical Steinway emitting alien sounds enabled by considerable internal doctoring with various screws and wedges.

Most often, I heard something resembling a large, deep-sounding bell that seemed to be plucked rather than struck. There was something jingly in there, as well as seemingly dampened keys that sounded a bit like a toy piano. Most fascinating was the way these sounds interplayed with the conventional piano timbres, creating all manner of fascinating juxtaposition and counterpoint.

If ever there was a concert for Cage skeptics, this was it. The wispy, quiet, short-breathed Cage music that has been often heard during the composer's 100th birthday year - in performances that spell out the notes with a you-figure-it-out attitude - seemed far away amid Tan's beautifully defined phrases, clearly etched formal signposts, and precisely voiced sonorities. As with great Mozart performances, Tan played Cage as if each of her fingers had its own individual brain.

It's often said that Cage's drug of choice was Asia. Even in this early work, that influence was apparent in the use of exotic scales, but with a sense of color and poetry that suggested music a step or two beyond Debussy, or a second cousin to Japanese composer Toru Takemitsu.

Part of their Asian character is having no typical sense of beginning, middle and end, so it made sense that Tan wouldn't have the sonatas and interludes spelled out in the program, or defined by pregnant pauses in her performance. Mostly, the sonatas and interludes were run together. It made sense.

Why couldn't the hipsters take it? Maybe they're not used to anything this good. Or maybe this free-of-charge concert was too easy to take for granted, given Van Pelt Auditorium's lack of door control. Premature departures are one thing, but people were also free to traipse in during the performance, talking aloud as Tan was playing. Not good.