"Knock knock." "Who's there?" "Knock knock." "Who's there?" "Knock knock." "Who's there?" "Knock knock." "Who's there?" "Knock knock." "Who's there?" "Philip Glass." Just about every music geek I know told that joke at least once in the late '80s. But tell it long enough—I insisted on doing the "Knock knock" part at least a dozen times—and you touch the core of how Philip Glass makes lush, captivating music on the piano, with orchestras, in opera houses, and even on amplified tabletops with his 1967 piece "1+1."

When listening to Glass, what seems initially childlike, tedious, or aggravating, or, god forbid, simple, unfolds into an alluring tapestry. Repetition, especially human-made repetition, opens the ears to tiny differences in rhythm and unfurls relationships among overlapping melodic lines. You get inside the sound.

Repeat the word "table" 30 times very quickly. The semantic meaning of "table" soon evaporates; saying "table" fast elides the start and end of the word, chiseling your utterance into an unexpected melodic shape. When you repeat, you eventually forget, and then, with only a whiff of the past, you begin remembering something new and possibly oracular: I know one sound artist who, at once inspired and repelled by Fox News during the 2007 Democratic presidential primaries, rapidly chanted "Obama Osama" hundreds of times every few days in order to induce a prophetic vision. (For what it's worth, he told me, "Obama's gonna win. Bin Laden has a serious leg injury.")

On paper, Glass does not radiate harmonic genius, yet he reinvigorates familiar harmonies by repetition and, at times, cataclysmic juxtaposition. Glass knows that with repetition, harmony molts into timbre, endowing sudden shifts in texture with a declarative, cadential power.

In his orchestral work The Canyon, much of the orchestra chugs along in a martial two-step until, out of nowhere, the percussion section erupts with startling, savage ferocity that jolts you out of your seat. By contrast, Mad Rush, originally written for organ but performed live by Glass on piano, is tender. Trembling, sentimental notes surrender to fevered chords in an easy-to-follow song structure. Miraculously, Glass makes the urgent flurries of notes amplify the gentle section, whose sweetness grows and blossoms.

Glass, in what could be called a "Play Solo Piano Anywhere but Seattle Tour"—he started in Spokane on March 31—plays Mad Rush and other pieces including a set of Études, "Knee Play 4" from Einstein on the Beach, and an excerpt from his opera Satyagraha (Thurs April 1, Washington Center for the Performing Arts, Olympia, 360-753-8586, 7:30 pm, $32–$43; Fri April 2, Kirkland Performance Center, 425-893-9900, 7:30 pm, $50). recommended