In their noon recital yesterday at Lisner Auditorium, local pianists Jessica Krash and Adrienne Sirken may have silenced the rustle of lunch bags, but they did little to move the earth.

Indeed, this program's interest rode on the two rarely heard four-handed pieces by Mozart and Schubert. For both composers the additional fingers at the keyboard gave license to a wider range and greater density of instrumental textures, perhaps even to symphonic writing.

And Mozart's Sonata in C, K. 521, certainly invites pianists to realms off limits to performers using only two hands, unless, of course, they're playing one of his concertos. The piece is delightful in the way that it outlines a simple melody and suddenly dazzles listeners with all sorts of appendages to the main theme. Lush arpeggios and thunderous chords intensify an abrupt digression to the minor, striking events that both women conveyed despite a few slips. Some fine teamwork distinguished the overlapping question-and-answer passage in the Allegretto. However, the phrasing and expression in the Andante were a bit unsubstantial.

Qualified as they were to grapple with Mozart's remarkable ideas, Schubert's diffuse Fantasia, Op. 103, D. 940, caused Krash and Sirken to lose their focus at points. In the opening, they gave a forceful presentation of an idea built around the octave leap, anticipating the piece's utter vastness. Schubert's ideas lend themselves more to digression and repetition than development; the performers must add coloration to make the material sound fresh and new. But while Krash and Sirken succeeded technically in their presentation, they fell short of interweaving this material.