Perched on the edge of a rocking chair with a score opened before her, Eleanor Sokoloff looks up into the air and shakes her head in time to the music.

"That's a girl," she says, her forceful alto overpowering the Beethoven. "I could use a little more top. Ah. That makes all the difference in a phrase."

The French cuffs of Sokoloff's 15-year-old student glide over the Bösendorfer keyboard. And then Sokoloff stops her.

"Well . . . ," she says with distaste and suspicion in her voice. "Why is that note so soft?"

Yen Yu "Jenny" Chen tries it a different way.

"No, that's ugly. You know why? It breaks the line."

Chen takes yet another stab at it.

"Much better," says Sokoloff.

This drill, the transfer of accumulated knowledge from master to student, is basically the one you hear in every studio at the Curtis Institute of Music. Except that this master has been doing it longer than anyone else.

Much longer. Eleanor Sokoloff has held essentially the same job at the world-renowned music conservatory for 73 years.

If you count back to the first time she walked through the doors as a frightened 17-year-old student, Sokoloff, 95, has been a presence at the school for nearly eight decades.

"She was always here," said former Curtis president Gary Graffman.

"She's kind of a colossal figure at Curtis," said Heather Connor, a student from 1992 to 1997.

And so, to get the full measure of the pedagogue, as peppery in her opinions as she is perpetually sunny and curious about life, you'd really need nothing less than a centenarian eyewitness.

Curtis being Curtis, the school has one.

"She stresses the fundamentals of piano playing and builds on top of that, as good teachers should," says Orlando Cole, 101, the cellist who matriculated at the school at its founding in 1924 and became an emeritus faculty member in 1995. "She's had innumerable fine players - I mean really world-class pianists - and they start with her and go on to other teachers who get credit for it. You know. That's the way."

Not always. Among those eager to give credit where credit is due are Leon McCawley, Charles Abramovic, Randall Hodgkinson, Craig Sheppard, Lambert Orkis, and Susan Starr - pianists of varying vintage, but all holders of big careers.

As piano teacher to non-piano majors, she also taught musicians famous for doing other things: former Philadelphia Orchestra concertmaster Norman Carol, violinists Aaron Rosand and Jaime Laredo, and violist Michael Tree.

How many students has she had? No one at the Rittenhouse Square school knows, and she's lost count.

"I can tell you this: More than 75 have played with the Philadelphia Orchestra," she said.