Looking out at the rows of empty seats at Merriweather Post Pavilion last night, Joan Baez wondered aloud if anyone's ego could go unbruised by the sight of something less than a full house. "Maybe Mother Teresa's or Mahatma Gandhi's," she said, "but I promise you a beautiful concert."

Baez delivered on that promise though the beauty more often lay in her singing than in her songs. At 41, she has never sounded better. Her pristine soprano has only improved with age, boasting greater depth, color and assurance.

As always, her voice proved ideally suited to traditional folk ballads as well as to some contemporary material written in a similar vein, like Bob Dylan's "Forever Young." But songs requiring more interpretive skill were much less impressive.

"Me and Bobby McGee" and Janis Ian's "Jesse" were pretty but expressionless, and Baez's own songs, which tend to be verbose and, depending on your politics, either pointed or preachy, are all cut from the same cloth.

Still, Baez's voice is a treasure in itself. Moreover, she seems quite content to be singing what she's chosen to perform, and to be talking about issues that matter to her. "Twenty years ago, I was the right person at the right place at the right time," she said. "Now I'm just the right person. I'll wait for everyone else to catch up.