Andrea Clearfield's Center City living room is part Swiss chalet, part Craftsman-style attic, an impossible cone-shaped space held up with dark timber beams and accented with a Mercer tile fireplace. It's nothing for the successful composer to invite a hundred or so strangers up to her third-floor lair to listen to musicians perform, from willowy pianists fresh from Carnegie Hall to grizzled folkies singing boxcar blues. All she asks is that guests remove their shoes before plopping down on her beige carpet.

It's not only that she wants to keep people from tracking in dirt, although the no-shoes policy helps. Her real motivation is to give audiences the experience of listening to music in the most relaxed, unprocessed venue possible. When everyone is sitting around in socks, "it just creates a mood," she says.

Clearfield, who is crowned by a froth of raven curls, runs one of the best-known music salons in the country, an eclectic gathering that is modeled on the great Parisian salons of the 19th century, where the likes of Liszt and Chopin tried out their compositions. She's been welcoming people into her living room nine times a year, for close to a quarter century, and was planning to hold a 25th anniversary concert there in September - until she learned the landlord was putting the house up for sale.

Clearfield has been populating her unusual apartment with musicians and music lovers for so long that the possible loss of the venue feels as momentous as the closing of any cherished city institution. While the salon had its beginnings in an earlier apartment, a one-bedroom unit on Spruce Street, it evolved into something magical when she moved into the high-ceilinged attic of a rundown house a block from the Kimmel Center in 2003. It was the perfect union of space and use.

The salon, Clearfield explains, was always meant as a sort of anti-Kimmel, and the garret apartment is as far from the polished grandeur of a concert hall as one can get.

First there is the matter of finding it. Clearfield's house is tucked away on an alley off an alley, a street so removed from the beaten path that even lifelong Philadelphians may be unaware of its existence; it appears almost like the street of magic supply stores in the Harry Potter books. (Best to visit for directions.)

Then, assuming you succeed in locating the house, there's the vestibule piled with shoes, the climb up the winding staircase, the traffic jams on the landings as equipment-lugging musicians reconnect with old friends, and, finally, the surprise of emerging at the top of the stairs into a soaring room that looks as if it were lifted from an Eakins painting. Sometime around 1910, a doctor with artistic inclinations created the unusually spacious aerie by combining three tiny rowhouses.

Musicians set up next to Clearfield's grand piano, while guests pay $10 for the privilege of securing a spot on the floor. Clearfield, a noted musician in her own right, sees herself as the salon's curator. At each event, she presents 10 acts that range widely across genres and geography. Sets last 10 to 15 minutes, then the performer hands off the mike and music stand. The acoustics, according to some musicians, are pristine.

There is still hope that Clearfield might celebrate the salon's 25th anniversary in her timbered living room. While Clearfield is acclaimed by Inquirer music critic David Patrick Stearns for her "compositional wizardry," she can't afford to buy the building, which includes a second apartment. But one of her regular guests, Ben Bingham, who specializes in sustainable investments, has formed a group to acquire the house and lease the attic back to Clearfield - before it goes on the market in the next few weeks.

The group has raised almost half the expected sale price. Bingham says they prefer to buy the building with cash, instead of a mortgage, so the investors would receive rental income. But they are open to various options.

The bones of the house, according to David Wickes, a salon regular who lived there as a child in the '60s and '70s, may date to the 1780s. The huge attic, created when the three trinities were combined, probably housed a painter's studio. Over the years, it served as home to an art school, a party room for Mummers, and a studio for a Philadelphia Orchestra cellist.

Clearfield has interpreted the bohemian space in a new way, much as the photographer Zoe Strauss did when she began holding exhibits under I-95's elevated roadway. By opening her home for concerts, Clearfield made a storied private room available to the public. Some 16,000 people have attended her salon so far, she estimates.

Clearfield says she learned about the attic's existence in 1989, three years after she started her salon. "I basically began to stalk the house," she recalls, sending Christmas cards to the owner in the hope of being allowed to rent the attic or buy the house. "My jaw just dropped when I saw it. I had a vision for the salon, and this was it. I just couldn't get it out of my aura."

But every time she came close to getting the house, it somehow slipped out of her grasp. Finally, in 2003, she received an e-mail from the current owner telling her the loft was available. She was trekking in Nepal at the time.

No matter. She instructed a friend to put down the deposit and move her furniture.

Since Clearfield founded her salon, when she was 26, several other local salons have sprung up, though few have the renown, or the deep bench of topflight musicians. Although she's more interested in showcasing performers who march to their own tune - including a surprising number of punk-inflected classical musicians - she occasionally picks ones who go on to the big time, like Jennifer Higdon, a flutist and composer who won last year's Pulitzer Prize, and Karen Slack, a soprano who appeared at the salon just before making her Metropolitan Opera debut.

They don't play for the money, yet Clearfield says there is a waiting list to perform. It's an opportunity, of course, to play for people who really know how to listen. But it's also the way the old attic acts as a repository of sound, gently cradling in its walls every note, from this evening and all the ones before it.

Contact architecture critic Inga Saffron at 215-854-2213 or