Pianist Alicia de Larrocha, last night at the University of Maryland's Piano Festival, provided a cool, restrained contrast to the extraordinary exertions of Dimitris Sgouros the night before. The evening was problem-free, bathed in radiance.

Not a note on her program was less than 200 years old, and not a note was originally composed for the instrument she played -- a modern Steinway. George Frideric Handel had the harpsichord in mind when he composed his Suite No. 5 in E (the one with the popular "Harmonious Blacksmith" Variations). So did Domenico Scarlatti for his 500-odd little sonatas, of which de Larrocha played a well-selected half-dozen.

Unlike some pianists who play this music, she did not try to ape the sound of the piano's ancestor. But she did translate to the piano keyboard the two essential qualities of the harpsichord's sound: the clarity and variety of texture that allow it to speak simultaneously in more than one voice. She kept the music to an 18th-century scale of dynamics, though she allowed herself some expressive gradations of sound unavailable on the harpsichord. She was graceful and witty in Scarlatti, solid and relatively square-cut in Handel, showing deftly the differences between these two composers, who were both born in 1685.

When she moved on to Mozart after the intermission, her style and sound were transformed. The fortepiano, for which Mozart composed, was a smaller instrument than the Steinway, less evenly voiced from one octave to another and less capable of loud or sustained tone. De Larrocha adapted perfectly not to the limitations of the old instrument but to the style Mozart adopted when working within those limitations. Her de'tache' playing was exactly right, setting off each note in relief with a bit of air space around it, like individual pearls in a necklace. And again, her playing was marked by a special kind of linear clarity, her left and right hands engaged constantly in dialogue, each with its distinctive voice.

The music was sunny, untroubled, deceptively simple to the ear, and she explored its intricacies masterfully without trying to impose on it more than Mozart had put there. Perfection is not possible in some Beethoven sonatas, but it is (at least theoretically) in Mozart's modest No. 9 in D and No. 10 in C. Last night, in this music, perfection was achieved.