"If I can make it until the 16th of this month, I'll be 74," said B.B. King at Wolf Trap Thursday night. "Here's to you," he added, raising a plastic cup and toasting all the fans who've kept him on the road for more than 50 years.

Headlining yet another multi-act summer tour, the legendary bluesman prefers to be seated throughout most of his concerts these days. But the qualities that have always been associated with his best performances--the declamatory, hand-in-fist vocals and the now elegant, now stinging guitar work--still make for an extremely potent combination. Potent enough, in fact, to draw numerous standing ovations from a rain-drenched crowd that had already spent three hours listening to the tour's opening acts--Indigenous, Tower of Power and Kenny Wayne Shepherd.

Even when leaning back in a chair, King can still make a jump blues jump, as he proved on "Let the Good Times Roll," and the relaxed setting allowed him to approach some other familiar songs in an intimate yet soul-stirring manner, particularly when he reprised "Nobody Loves Me but My Mother," "Outskirts of Town" and "How Blue Can You Get?"

As always, the answer to that question often came from Lucille, King's famous guitar and constant companion, who spoke out between the verses with a mixture of mournful eloquence and impassioned shouts. While too much of the show was devoted to introducing and reintroducing members of King's eight-piece band, and to some lightweight funk, the seasoned ensemble frequently supported the bluesman with a time-honored mix of insistent horn charts and soulful Hammond organ grooves.