Music : A Performance of Conviction by Boston Handel & Haydn

It seemed a tenuous conceit: a concert built around the figure of a late-18th-Century arts patron, the Dutch-Austrian Baron Gottfried van Swieten.

But during every measure of Handel’s “Ode for St. Cecilia’s Day”--presented in the clever gussying-up, to suit the contemporary taste, that Swieten commissioned from Mozart--one had to be convinced of the validity of a tribute to Swieten’s transfiguring gift to music history: the conviction, unheard of in his day, that the past held treasures of limitless worth.

And it didn’t hurt to have Mozartized Handel presented as persuasively as it was on Saturday in UCLA’s Royce Hall by the chorus and period-instrument orchestra of Boston’s Handel & Haydn Society, conducted with forceful, stylish mastery by Christopher Hogwood.

The only possible complaint concerned Dryden’s English text. You don’t translate lines as shattering as “The trumpet shall be heard on high / The dead shall live, the living die / And music shall untune the sky.” But translate them, and the rest of Dryden’s poem, into a lumpy German Swieten did. And all survived, thanks to Handel’s sublime musical imagery.

The 18-member chorus proved remarkable for its flexibility and purity of intonation and, less predictably, for the heft it brought to the score’s grandest climaxes.

The two vocal soloists, Britons both and paragons in their field, were tenor John Mark Ainsley and soprano Lynne Dawson, the latter a singer of cherishable warmth of tone, accuracy and expressivity.

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Earlier, the chorus and a smaller orchestra distinguished themselves in J.S. Bach’s motet “Singet dem Herrn,” to which Mozart was introduced by the antiquarian Swieten, while the orchestra shone in a score commissioned by the Baron, also a patron of the avant-garde: a characteristically busy, quirky Symphony in B flat by C.P.E. Bach.

Sandwiched between these two was Mozart’s striking Papa Bach-style organ Fugue in G minor, K. 401, for four hands, fierily played by Hogwood and John Finney.

The Handel & Haydn Society played in Costa Mesa Saturday night under the sponsorship of the Orange County Philharmonic Society.