When the veteran period-instrument ensemble the English Concert dug into Vivaldi's "La Follia" Trio Sonata at its Library of Congress program Thursday, this customarily elegant group seemed to be channeling the brasher, more risk-taking approach of many Italian period-instrument bands, with boisterous attacks, daringly elastic phrasing, extravagant ornamentation and even some drumming on the double-bass. If ensemble unity was pushed to its limits, conductor Harry Bicket made sure the improvisatory verve didn't undermine cohesion.

Early-music celebrity violinist (and former English Concert member) Rachel Podger held focus here with her silvery tone and commanding virtuosity, as she did in Vivaldi's "Il Grosso Mogul" Violin Concerto. Her harmonically exploratory, third movement cadenza sounded freshly composed on the spot, and her dreamy, exotically pitch-bent treatment of the concerto's slow movement (against very Middle Eastern-sounding color from the droning bass and skittering arpeggios on the lutes) proved an atmospheric delight.

The ensemble was its more restrained self in a spare reading of a Vivaldi cello concerto (with Jonathan Manson the eloquent and warm-toned soloist) and in quietly supportive work in Monteverdi's "Lamento d'Arianna" and Handel's "O numi eterni" Cantata. Both solo dramatic works are tailor-made for the superb mezzo, Alice Coote (who returns to D.C. for a Vocal Arts Society recital on Nov. 4). The qualities that make her such a distinctive performer - the bittersweet tang and tragic weight in the tone, the dark and forthright chest voice, the emotional candor in her phrasing - ensured that the Monteverdi and Handel (as well as a vividly inflected set of Dowland songs) were riveting experiences.