Throughout his 20-year career, Van Morrison has been both a brilliant vocalist and a moody recluse, a meditative mystic and a fiery R & B shouter. He was all of this last night at Constitution Hall -- his first D.C. concert in 11 years. He proved he is still one of the best singers of his generation as he spread his rich, resonant tone into every corner of his ballads and then focused his attack into hard-hitting accents on his uptempo soul tunes.

Nonetheless, the show was marred by a horrible sound mix that obscured lyrics, muddied instruments and often allowed the drums to drown out the melody. Moreover, Morrison's energy seemed to drift in and out of focus, as he grabbed hold of some songs but only went through the motions on others. Morrison is legendary for being an erratic live performer, and he never seemed to catch fire last night.

He began with a perfunctory medley of five of his earliest hits, including "Gloria" and "Brown-Eyed Girl." He didn't seem to wake up until the seventh number, which segued from John Allair's organ solo on "Green Onions" into Morrison's blustery soul shout on the R & B chestnut "I Can't Love You by Myself." After the medley, Morrison mostly stuck to his more spiritual compositions of the '80s, ignoring pleas for his better-known material from the '70s.

He was at his best when he combined his mystical tendencies with his love of American R&B. "Tore Down a la Rimbaud," for instance, featured meditations on venerable poets and painters -- but the nine-member band gave it a rocking dance beat. "Haunts of Ancient Peace," a ballad, effectively evoked old pastoral England, but it was broken up by an aggressively inventive tenor sax solo by Pee Wee Ellis that reminded one more of Coltrane than Wordsworth. Morrison's best moment came on a romantic ballad, "What Would I Do." As he pondered a future without his lover, he skillfully shifted from contemplation to desperation to determination, and his big voice seemed to grow bigger and bigger.