Even the most devoted classical musicians don't necessarily play their instruments every single day. So it's hard to guess what flutist Mimi Stillman stands to accomplish by recording, on video, Debussy's elusively melodic flute solo

Syrinx

every day (or close to it) for a year and posting the results on her website.

"A year is a long time, it's true. I don't know where it will take me - or what I will find in the music. But I know I'll find something," said the founder and artistic director of the Philadelphia-based Dolce Suono Ensemble, who has already posted Syrinx videos for Israel and Italy on www.mimistillman.org.

"Sometimes you have an audience that's unexpected," she said. "In this tiny town in Tuscany, cats and dogs came out to listen. Birds often start singing if there's a flute nearby."

And if she's stuck in an airport and has to video Syrinx there? Well, she already lost a day or two while traveling between Europe and America. But an airport video could happen: In years past, she played Mozart for stranded fellow passengers.

If there's a requirement for her Syrinx venues, it's relative quiet. No Washington subway for her. That's where high-profile violinist Joshua Bell tried busking and was largely ignored - a widely reported incident that, for Stillman, proved nothing. "People were on their way somewhere!" she says.

Stillman, now 30, hatched her Syrinx-a-day idea as a response to Debussy's 150th birthday this year, and started on the actual date, Aug. 22. Because the French impressionist composer (1862-1918) had a relatively modest output that's performed regularly, anniversary celebrations are beginning to look beyond the typical.

Syrinx has been transcribed for trumpet. Stillman's own Dolce Suono Ensemble season will begin with "Debussy and Jazz" (Oct. 21, at the Trinity Center for Urban Life), pairing the urbane French composer with Jelly Roll Morton and the modern jazzman Claude Bolling. Next year, in April, she'll pair Debussy and his baroque-period ancestors.

Such devotion from Stillman, who entered Curtis Institute of Music at age 12, isn't surprising. She wrote a master's thesis (as a University of Pennsylvania doctoral candidate in history) on the impact of Asian music on the composer. Beyond that, flutists can't help but be drawn to Debussy, given his keen relationship with the instrument.

The 1894 Prelude to the Afternoon of a Faun, a major breakthrough for Debussy that was also considered the epicenter of 20th-century music, begins with a languid flute solo, written not in the instrument's most brilliant range but in a lower register that Stillman describes as "smoky."

The 1913 Syrinx, written a few years before the composer began suffering from brain cancer, was originally to be incidental music for a play, performed offstage as the god Pan mourns the loss of the nymph Syrinx. Aside from its mythological subject matter, Debussy's composition has its own myths, having supposedly been written originally without bar lines - the most basic musical signpost - and on a napkin. However it came about, the unaccompanied 21/2-minute piece feels surprisingly complete unto itself.

"It's so beautiful. In a very short time it has a real shape, with different sections that reach a definite climax that quickly dissipates," said Philadelphia Orchestra associate principal flutist David Cramer. "It's the kind of piece that, even if you plan meticulously what you're going to do, you play it differently every time. If you're going to pick one piece to play every day . . . that's a good one."

Finding interpretive variety in masterworks is the central challenge of any classical music career. Luckily for Stillman, Syrinx has much poetic ambiguity, hovering as it does around certain key signatures without really alighting on them.

Still, might boredom be inevitable? In anticipation of that, Stillman is looking to subject herself to a variety of stimuli, such as tracking down the play for which it was written (Psyché by Gabriel Mourey, listed in some sources as unfinished) and playing one of the wooden flutes of Debussy's own time.

Already, she played the piece in the resonant acoustic of Sant'Anna in Camprena, Italy (which appeared in the film The English Patient), where each note had such a long decay time the flute no longer sounded unaccompanied. Just as some of Bach's unaccompanied works have had accompaniment added by later composers, might Stillman try harmonizing Syrinx?

A possibility, she says. Along with anything else one can think of - one reason fellow flutist Cramer particularly looks forward to comparing Stillman's first and last performances at the end of the year.

Certainly, different settings can bring out different aspects of the music. "In Jerusalem," where she recently visited, "all of Debussy's winding arabesque motifs felt like a Western imaging of the Orient, which, for them, may have been anything east of Greece," Stillman says. Some of Debussy's busier passages also suggest Jewish folk music to her, and some of his less-melodic laments resemble Muslim chant.

Such musical parallels shouldn't be surprising. An obsessively meticulous composer (and notoriously difficult man), Debussy often seemed in search of something elemental in his music - one thing that no doubt led him to the flute.

"You know, the flute is one of the most ancient of musical instruments," says Stillman. "They've found flutes made from leg bones from 40,000 years ago. There's an extremely ancient, mythical, folkloric quality about the flute - that Debussy knew would be there."