The Washington Chamber Orchestra opened its all-Mozart program at Lisner Auditorium last night with the Symphony No. 24 in B-flat. The piece isn't the best evidence of the composer's genius, but Alvin Lunde and his players brought out much of its charm.

There was clarity of attack from the strings in the allegro spiritoso, some fine French horn playing in the andante and an airy momentum in the fleet-footed finale.

The evening was downhill from there--and a bit of a toboggan ride at that. Adrien Meisch, the ambassador of Luxembourg, was soloist for the Piano Concerto in A Major, K. 488. After intermission, he was joined by Evelyn Swarthout for the Concerto for Two Pianos in E-flat, K. 365.

The ambassador has an aptly light touch and a respectable trill. In the A Major concerto, however, these qualities were overshadowed by uncertain articulation, jumpy rhythms and a penchant for keeping eyes glued to the music, making for moments of muddy ensemble.

Swarthout brought some technique and authority to the double concerto, but she and Meisch couldn't always keep themselves together or stay with the orchestra.

The performance might have been better if pianist Lili Kraus, originially scheduled as a soloist, had not become ill and canceled.