The Library of Congress' week-long festival celebrating Brahms' 150th birthday opened last night with two contrasting performances that startlingly illustrated the electric impact the composer must have had when he emerged at 20 as the great new hope of German music.

First, pianist Detlef Kraus performed five works from that early period based on baroque dance forms, including two gavottes that were only recently discovered and another that is a vaguely focused transcription of the gavotte from Gluck's "Orfeo ed Euridice." These works showed a bold, inventive mind that had yet to find its own voice.

Then, there followed that propulsive, ardent, eminently Brahmsian Sonatensatz for violin and piano that also came when he was 20. This was written just before Robert Schumann discovered Brahms and launched his career. It is one of the expressive voices of Brahms that would last for much of the rest of his career. Here, in this C-minor work, are the seeds of Brahms' masterpiece in that key, the First Symphony, which would come more than 20 years later. No wonder Schumann was astounded at what he heard.

The Sonatensatz and the serenely lyric First Violin Sonata were played by violinist Robert Gerle and pianist Marilyn Neeley. Gerle's playing was idiomatic and understated. Neeley handled the technical challenges of the piano part--after all, Brahms was a piano prodigy--with assurance.

Then Kraus returned to play the knuckle-busting, herculean Variations and Fugue on a Theme by Handel. The performance was not the dazzling virtuoso feat that Rudolf Serkin brought off in this work here several years ago. It was, appropriately enough, rather like the description Schumann's daughter Eugenie once gave of Brahms at the piano: "To hear Brahms play his own works was, if not always satisfying, at any rate in the highest degree interesting. He brought out all the themes emphatically, with a tendency, which was characteristic of his playing, towards slightly irregular accentuation."