MUSIC REVIEW : Brothers Engineer a <i> Coup de Theatre </i> With Guitar : Concert: One almost hopes for a mistake upon hearing the seamless virtuosity of the Assads of Brazil.

After hearing a concert by the Brazilian classical guitar duo of Sergio and Odair Assad, one is tempted to suggest they should make a few mistakes on purpose. The surface sheen of their virtuosity combined with their impeccable coordination tended to mesmerize the poor listener. A minor flaw here or there would remind everyone of the human effort behind such seamless music making.

The two brothers made their local debut Sunday night at the East County Performing Arts Center with an unusual program, largely 20th-Century music with an emphasis on South American composers. Notable were a pair of emotionally charged works by Argentine Astor Piazzolla and three short pieces by Brazilian Egberto Gismonti.

Piazzolla’s essays elicited a wide range of instrumental color from the duo as well as a host of rhythmic subtleties. These evocative, sensual pieces also evoked the guitar’s traditional role as the instrument of choice for serenading lovers, an icon thoroughly ignored by Andre Jolivet’s four movement “Serenade.” Fortunately, the duo handled Jolivet’s dissonant abstractions--the composition has “serious music” stenciled over every phrase--with aplomb, and made his expressionistic clusters sound almost sweet.

With the opening set of three fluent sonatas by Domenico Scarlatti, the Assads established their trademark: a quick, lightly plucked sound woven into a dense surface texture. Although their absorption in the music distanced them from the audience--at first a distraction--the intensity of their devotion to the music’s demands could hardly be faulted.

They won high marks in technique for polishing off with apparent nonchalance Pierre Petit’s vibrant Toccata and Alberto Ginastera’s demanding “Pequena danza.” Two transcriptions of Debussy piano works, Prelude and “Passepied,” showed their skill at building well-balanced pastel harmonies.