Kong Xiangdong, pianist, City Hall Concert Hall, Thursday, July 8 THURSDAY'S concert by the technically astonishing Kong Xiangdong posed the question: Can the best-selling performer of the jazzy Yellow River Concerto with his horde of bobbysox fans in the audience plumb the depths of Brahms and Rachmaninoff? Can he be an artist as well as a Hongkong household name? The answer was mixed. The muscular 24-year-old was certainly a crowd-pleaser. As fans leaped on the stage with flowers asking for an autograph on a laser disc, he warmed to the occasion - playing a Chopin waltz with the meter of a Parisian can-can. He also played the Liszt Spanish Rhapsody without any rhythm at all. The fingers were absolutely dazzling. Kong can play a series of 32nd-note octaves with a breezy easiness. But the music was cheap, it was a rather conscious pandering to the audience. Kong can also be lyrically sensitive when necessary. Two other encores, from Tchaikovsky's The Seasons, were played with all the right care and tenderness. (The encores were something of a marketing tool, since his first recording with RCA will be the complete Tchaikovsky piano music.) But can Kong play more serious music? The Mozart K. 282 was lyrical, but almost unduly intense. The Schumann Arabesque was whizzed through with little contour but much fine technique. One had instinctive doubts that someone so young could play Brahms' final piano works. But Kong pulled out all the stops - almost like organ stops - to play with a semblance of poetry. Yet even this poetry was energetic. In the intermezzi which demanded a chorale-like sublimity, Kong played them as if it were the poetry of Dante's Inferno. At his age, Kong is entitled to his impetuosity. But his voice was hardly the voice of Brahms.