The Beethoven Society launched its new season with performances by pianist Thomas Pandolfi and mezzo-soprano Diana Burson Ayerbe at the West German Embassy last night. Both artists performed with undeniable brio, but on more than one occasion youthful zest obscured intelligent performance practice.

There's nothing wrong with wringing the power out of every forte in a Scarlatti sonata, as Pandolfi did in the A Major Sonata, L.483, and the D Major Sonata, L.463, but it's always a good idea to hold a little back for the quieter movements. For some reason, Pandolfi appeared loath to do this, and the performance suffered accordingly. A similar lack of subtlety marred the inner voices of Schumann's "Romance" in F-sharp, Op. 28, No. 2, and the intricately woven "Aufschwung," Op. 12, No. 2. By contrast, Pandolfi was well suited to the no-holds-barred bravura of Chopin's "Heroic" Polonaise in A-flat, Op. 53.

Ayerbe got off to a similarly rough start with Mozart's "Non so piu cosa son" from "The Marriage of Figaro" -- she might have done better leaving this piece until her voice had warmed up. But the Barber songs that followed and the "Cinco Canciones Negras" by Xavier Montsalvatge were fair testament to this singer's lyric and dramatic gifts.