Closing in on its 15th year, Jethro Tull endures, its enveloping progressive rock as unique and distinctive as ever. Before 10,000 satisfied fans at the Merriweather Post Pavilion last night, the British quintet provided a concise and fast-paced overview of a career that grew out of Cream-derived hard blues (still evident on "Hard Times" and "Aqualung") to include light favored jazz, hard rock and a fervent updating of the English ballad traditon.

As always, singer/songwriter Ian Anderson was the chief visual element, though his stage demeanor was decidedly mild compared with the halcyon days when he seemed to enjoy St. Vitas' Dance. With the band dressed like refugees from the Renaissance Fair being held in Columbia, Anderson projected his classic minstrel image, convincingly delivering the intelligent, concerned lyrics that have characterized the Tull sound as much as Anderson's insistent flute and Martin Barre's liquid guitar lines.

Despite clever time changes and Anderson's spritely word weaving, a sameness crept into the 22-song show. The once-fresh synthesis of English folk melodies with classical motifs and rock hardware seems a bit dated, though it does provide a steady frame for Anderson's electric muse. Still, the bittersweet "Too Old to Rock and Roll, Too Young to Die," was rendered invalid by the passion and affirmation of the band's overall performance.