There was magic at the Corcoran Gallery last night as museum relics were transformed into living treasures in full view of a cheering audience. The famed Paganini Stradivari violins and viola were played for the first time by their new custodians, the Cleveland Quartet. It was a momentous and beautiful occasion.

The best of the evening was Beethoven's Quartet in B-flat, Op. 18 No. 6. With this piece, the not yet 30-year-old Beethoven greeted the 19th century and its emotion already strains the elegant form of the classical quartet. The Cleveland's interpretation was a lesson in performing music that presaged the romantic sensibility for an audience that has already absorbed and bypassed it. And in a concert where the instruments themselves might have upstaged the players, these musicians shone with distinctive musical personalities of violinists Donald Weilerstein and Peter Salaff, violist Atar Arad and cellist Paul Katz.

The almost negligible first theme was ravishing in sheer voluptuousness of tone, and this beauty remained throughout the simple grace of the scherzo and the Haydenesque dynamics of the final allegro. There was an eerie insistence in the softness of the finale, a feeling of serenity that returned twice near the end as a delicate memory.

Ravel's Quartet in F Major followed. The waves of color in this impressionist score can hide its musical structure, and here they almost drowned it. The playing was fine and the tone had an attractive, Fauvist richness. The reading was rhythmically too free, however; and the result in the first three movements was a series of lovely voices saying little to each other. All this notwithstanding, the last movement was powerful and moving.

The program closed with Brahms' Quartet in A minor, Op. 51 No. 2. Like the Ravel, it was not a performance free of flaws, but these are hardly worth mentioning after such a passionate reading. It is a tribute to the superb musicianship of the Cleveland Quartet that the evening was so successful even with instruments new to the players. And these are no ordinary instruments, but among the most precious in the world. The pressure was great on the musicans, and the beauty of their music will only grow with their custodianship. The Paganini Stradivari are in very good hands.