As Scheide told the story at the church Jan. 22, she was living in San Diego when a friend, a flute player with the San Diego Symphony and a Czech, organized a trip to Prague so that her Californian students could attend an intensive, weeklong master class with Vokalkova. Scheide went along simply because she has never been to Prague, and she and Vokalkova hit it off at once.

They easily picked one another out, Scheide said, because they were the only adults in the room.

Vokalkova is spending a few weeks this month visiting both Scheide and Philadelphia. Last week, they began recording their second joint CD at Chestnut Hill Presbyterian Church — their first, a selection of works by Mozart and his father, arranged for flute and organ, was released in 2002 — and on Sunday they will perform a recital at All Hallows. The use of the space, and the resonant acoustics that result from its bare stone walls, is a gift of sorts from the church in recognition of the work Scheide puts in the rest of the time.

The concert is free, though donations will be accepted, and the program is a creative combination of the familiar and the not-so-familiar.

The repertoire of every instrumental soloist would shrink considerably without the music of Johann Sebastian Bach, but wind players would probably be at a particular disadvantage. While composers in the 19th century produced reams of chamber music for piano and violin, they produced few if any important chamber pieces or concertos for flute, even though, as Vokalkova says, the instrument reached its modern form at that time.

To fill their programs, solo wind players — and harpsichordists, too — have to either reach back to the 18th century or forward into the 20th, when composers began writing for their instruments again.

Sunday’s program will feature a sonata for flute and harpsichord and a partita for solo flute by Bach, as well as two pieces from the French Baroque, and, most interesting of all, a little-known sonata by a little-known Swiss composer, Marguerite Roesgen-Champion, who lived from 1894 to 1976.

The composer is so obscure that she does not even have her own Wikipedia page, but her sonata is attractive, impressionism-tinged music with a lovely adagio and a sparkling rondo finale. It deserves to be better known, and, one may hope Vokalkova’s performance will spark greater interest.

“I think Zofie’s playing is a very pure style,” Scheide said. “I think it’s a lot different from many American flutists.”

Materials count for much in producing that purity; Vokalkova plays a flute made of gold, which, she said, produces a darker tone than the silver or titanium used in other instruments.

“I like 14-carat gold because 18 is too soft,” Vokalkova said. “Twenty-four is too much.”

Scheide, too, takes care with the materials she uses in her harpsichord. Many players insist on the just the right woods for the case and soundboard, she said, but when it comes to the actual, sound-producing point of contact, where the plectrum hits the string, they settle for modern synthetics. Scheide insists on 100 percent bird quills, which of course were the material of choice in the 18th century. Vulture works best, she finds, and she buys her quills from a builder in Germany who keeps the birds on a farm.

Lest listeners feel guilty, she assures them that no bird was harmed in the making of her instrument.

“He just loses a couple of feathers,” she said. “Materials are everything.”