The Manchester String Quartet --

all National Symphony Orchestra members -- billed last night's concert at the Washington Cathedral "Music of Bach's Time." The title proved a little deceiving as pleasant works by Vivaldi and Dittersdorf and significant quartets by Haydn and Mozart joined on one program.

Three Vivaldi selections opened the concert with an excellent demonstration of polished ensemble work. Immediately evident were the group's warm sound and careful phrasing and articulation. The delightful E-Flat Quartet of Dittersdorf, a renowned figure in his day, was played with charm and sensitivity to the music's tricky tonal plan. First violinist Hyun-Woo Kim was first rate in Haydn's D-Major Quartet, Op. 76, No. 5, one of his final masterpieces. The beautiful slow movement and the finale's lively dance tune were both crisp and airy, but inner voices of the allegro and minuet seemed slippery and insecure.

Commissioned by the king of Prussia, an avid cellist, the works of 1789-1790 are Mozart's last -- and perhaps finest -- string quartets. There were some pitch problems in the performance, but the group successfully projected the concerto style of the first movement, the upper string figurations of the second, and the fourth's lovely modulation sequences.