The concert part of the week-long 13th Annual University of Maryland International Piano Festival and Competition opened last night with Agustin Anievas in a program that ended with Brahms' dauntingly tough Paganini Variations.

Even Franz Liszt himself never produced a work that was more difficult to play. Those two books of 30 variations on the theme of Paganini's last Caprice for unaccompanied violin--the same one Rachmaninoff used about 75 years later for his enchanting Rhapsody for piano and orchestra--put the player through just about every trick in the book. One very eminent pianist confessed recently, "I don't play it because it's too hard."

Not so for Anievas, however. This fairly young American virtuoso has nothing if not agility. His fingers moved with assurance last night through Brahms' most intimidating double octave leaps, complicated figurations, glissandi and . . . you name it.

He has enormous volume when needed, but, also, the most rippling delicacy.

Anievas' image as a high-powered virtuoso, however, is a bit blurred by his reticent manner on stage. Last night, though, the audience at Tawes Theater finally was charmed when he disarmingly announced before diving into the Brahms that he was going to take off his jacket--a reasonable reaction to the theater's inadequate air conditioning.

It was a considerable sign of Anievas' versatility--and of his depth as an interpreter--that the other high point of the evening came in a work utterly unlike the Brahms variations. It was in the sublime, metaphysical slow movement that ends Beethoven's piano Sonata in C-minor, Op. 111. This movement--a lyric theme with variations--concludes his last sonatas and is the valedictory to the piano of the man who wrote probably more great music for the instrument than any other composer.

To bring it off, a pianist must be able to sustain a long, slow lyric line almost to the breaking point, and he must be aware that the slightest harmonic deviation may turn out to be of extraordinary import before the work is over. Anievas showed real authority.

Thus it was puzzling that the tempestuous allegro that comes first was bland--its mercurial moods ill-defined. Perhaps the idea was to understate the music, but the movement is of such epic proportions that understatement doesn't work.

There were also three Rachmaninoff preludes, played with drama and rich sonority. And the opener was the Mendelssohn Prelude and Fugue in E-minor; it is modeled on Bach but doesn't quite have that master's touch. Mendelssohn's greatest gesture toward Bach was not to copy him--it was, as Mendelssohn the conductor, to rescue the St. Matthew Passion from 75 years of obscurity.

Anievas, by the way, was the third pianist this viewer has seen in less than two weeks who has played a Bo sendorfer grand (Garrick Ohlsson and Bella Davidovich were the others). Is Steinway in trouble?