About six months ago the Cleveland Quartet, which has been at the top of the chamber music world since it was founded in 1968, took a pretty drastic step. The players disowned their instruments, adopting the four matched strings owned by the Corcoran Gallery that were assembled by that virtuoso of virtuosos, Niccolo Paganini. It was a chancy undertaking. They had to commit themselves to the instruments before they knew that they would work. The cello, in particular, was in questionable shape.

Well, they need worry no more. They played the strings last night at the Corcoran's Hammer Auditorium, and the instruments are clearly glorious.

Apparently Paganini went out of his way to pick instruments that were not only beautiful, but also complementary in their transparency and luster. The Cleveland has always made a beautiful sound, but as cellist Paul Katz noted last night in a conversation, it has "a sheen" with these Strads that it never had before.

It came into its fullest dimensions in the wide-ranging sonorities of the Dvorak "American" Quartet and the Mendelssohn Capriccio, which was an encore. The sound is very large and has great vibrance -- almost symphonic in sound.

The interpretation of both of those works was equally symphonic in phrasing. The players are positively wallowing in their new sound. It is short on gutteral offshoots and long on resonance -- and the balances are exquisite. These are instruments that don't have to be pushed very hard to get into full voice.

The Haydn "Serenade" Quartet and the Beethoven "Serioso" suffered from the lack of air-conditioning, which got going at intermission. Both players and listeners suffered.