As a young composer, Handel made demands on the human voice that, years later, the mature Handel wouldn't have thought of making. His early secular cantata "Apollo and Daphne" is mild in this respect, but even here the baritone role of Apollo has moments of almost coloratura agility that are a challenge to the most athletic of voices.

Jan Opalach took on that challenge with mixed results Thursday night. The cantata was the focus of the Handel Festival Orchestra's program at the Kennedy Center's Terrace Theater, and Opalach sang it with all the posturing and bravado the score called for. He delineated Apollo's awakening love and commitment with nicely shaped vocal shading and came to terms with Daphne's escape with dignity. He did not, however, manage the ornamental business that Handel decreed for the top of his range with any particular grace or ease.

Soprano Carol Webber sang the smaller role of Daphne with musical finesse but with a vibrato so overbearing that it eclipsed many of the nice things she was doing.

The orchestra did not sound as well prepared as it generally does for these concerts. There were moments of uncertainty at cadences and ensemble problems from time to time in the cantata and in the concerti grossi that also were played. Stephen Simon, however, conducted with his accustomed assurance and maintained momentum and a nice instrumental balance.