What does it feel like to play the largest functioning organ in the world?

"It never ceases to be thrilling," says Peter Richard Conte, the Grand Court organist at Macy's in Center City. The organ he has played for the last 27 years is the magnificent Wanamaker Grand Court Organ. The Wanamaker flagship store of years past is now a Macy's, but the organ remains, a singular Philadelphia treasure.

The Friends of the Wanamaker Organ will hold their 23rd annual Wanamaker Organ Day on Saturday with concerts, movies, and tours of the organ chamber. Built in 1904 for the St. Louis World's Fair, the organ, then with about 10,000 pipes, was bought five years later by John Wanamaker for his store.

Because the Grand Court - the multistory atrium at the store - was so vast, he decided to enlarge the organ. At 287 tons, it's a behemoth. And with 28,482 pipes, six keyboards, and 729 stops, it's understandable that Conte describes the console as being "like a cockpit of a large aircraft." Thanks to the support of Macy's, Conte says, the organ is "in the best shape of its life."

As with most pipe organs, the pipes you see aren't the ones that actually make sound. Those are hidden behind the facade. Ray Biswanger, executive director of the Friends of the Wanamaker Organ, says, "As powerful as the Wanamaker organ is, with pipes spread from the second through seventh floors, much of the power of the experience comes from masses of pipes that have been moderately voiced to form very lush and rich choruses of tone." Generations of shoppers can attest to the effect.

The organ's fame is global. "When I tour Europe and mention that I live near Philadelphia," Kathleen Scheide, organ professor at Westminster Choir College, wrote in an email, "musicians everywhere (and not only organists) immediately ask about the Wanamaker organ."

The location of the organ is also singular. Alan Morrison, chair of the organ department at Curtis Institute, sees it as culturally important: "With fewer people attending religious institutions these days, coupled with the embarrassing absence of music in schools, I think having this instrument in a major public setting is crucial to the cultural enhancement of our community. If people don't hear classical music at school or anywhere else, they are able to hear it while shopping."

Wanamaker Organ Day begins with an audiovisual tribute at 10 a.m., followed by a free concert at 11 a.m., simulcast on WRTI-FM (90.1). A ticketed silent-movie concert, at which organist Walt Strony will play the third-floor Wurlitzer organ to accompany a Laurel and Hardy flick, is at 2 p.m. in the Greek Hall Auditorium at Macy's.

At a second free concert at 5 p.m., the Wanamaker organ accompanies a chorus in a concert of French music. The public can meet the performers after these concerts on the second floor near the console.

A ticketed evening concert at 8 p.m. will feature organists Conte, Strony, Monte Maxwell, and Andrew Ennis. The ticket price includes admission to the afternoon silent movie and light refreshments in Greek Hall before the concert. The highlight of the concert will be a four-hand arrangement by Ennis of Respighi's Pines of Rome. Conte and Ennis will give a teaser of the work at the first concert.

Of course, Wanamaker Organ Day isn't the only time to hear this massive instrument. There are free concerts daily throughout year - except Sundays - and the public can tour the console area after each performance. "The Grand Court is Philadelphia's living room," Biswanger said, "and the Wanamaker organ is, in essence, the voice of the city of Philadelphia."

Wanamaker Organ Day at Macy's, 1300 Market St. Tickets: $10 for 2 p.m. Wurlitzer concert; $50 for all ticketed events (2 and 8 p.m.). Information: 484-684-7250 or www.wanamakerorgan.com.

Elivi Varga is a professional flutist living in Manayunk.