Last night's steady shower of musical riches by the Vermeer String Quartet and pianist Walter Klien at the Terrace Theater was a happy last-minute event.

It was happy, that is, in all but one respect -- and that was the serious illness of cellist Leonard Rose, which prevented him from playing a solo recital as scheduled.

When it became clear recently that Rose would be unable to come, Kennedy Center artistic director Marta Istomin had the fine idea of combining on a single program the quartet, which will perform a recital at the Terrace Friday night, and Klien, who will play an all-Mozart program tomorrow.

The Austrian pianist and the American quartet had never worked together before, a circumstance that in no way inhibited their bold, sweeping account of that most symphonic of piano quintets, the Schumann. It was a dashing and confident rendering of Schumann's mini-concerto, a work so bursting at its expressive seams that it seems almost orchestral. Klien, in particular, brought considerable passion and vitality to the job.

And if the Schumann leaped beyond the normal bounds of chamber music intimacy, the same was even more true of the other work -- Beethoven's herculean Quartet No. 13 in B-flat major -- played as first written, with the colossal Grosse Fugue as the finale.

From its beginning, that 15-minute contrapuntal Everest of a movement was problematic -- almost too towering a creation to be combined with anything else. The composer, in fact, was finally persuaded to write another, more modest, finale -- which is the one usually played. The idea was to do the fugue alone, and Beethoven couldn't even decide what was the most effective instrumentation. He made a brilliant arrangement for two pianos, and it is also common these days for it to be played by full string orchestra.

Last night's performance did not settle the problem. One got the feeling that the Vermeer players, who are based in Northern Illinois University in DeKalb, were holding back in Beethoven's five earlier movements, waiting to hit the musical ground running with their slashing opening to the fugue. This was understandable, because the fugue is a mercilessly hard piece to play. They laid on all the tension and sonority and rhythmic impact they could summon.

The result was majestic, but there was a discrepancy between the attacks in the fugue and the blander approach, for instance, to the quartet's shadowy little Presto movement and even to the sublime repose of the Cavatina, that musical godfather of Mahler's symphonic adagios.

Realistically, the rigors of the Schumann and the Beethoven may have been too much for one program. But there were many thrills in hearing the players make the effort.