Napoleon Carl Davis and the Hongkong Sinfonietta, Queen Elizabeth Stadium. January 30 MOMENTS of genius are not enough to justify a work's revival. Abel Gance's silent film Napoleon's status as a work of genius is questioned by critics for his portrayal of Napoleon's character. However, Gance's use of the camera, freeing it from tripod and rail, mounting if however and wherever he liked, was brilliant. It forced audiences to become involved in the action in ways that they had never experienced. It is Carl Davis's symphonic score, however, that has assured the revival. Its success revolves around two factors. The first was choosing Beethoven for the backbone of his score, recognising the composer's instinctive empathy with the issue. Secondly, Davis chose not simply to lump chunks of Beethoven together, salting them with a few grains of other composers. Instead he quoted from Beethoven, sometimes verbatim at others drawing from the thematic material, mixing Beethoven's ideas with other themes. The effect was seamless, the music riveting attention to the screen. Only in the storm scene did Davis's score seem out of joint. Gance shows surf breaking, the camera submerged in windswept seas but it is hardly a storm. Yet Davis unleashed the weight of the second theme in Beethoven's ''Pastoral'' symphony's storm movement. The Hongkong Sinfonietta gave a performance full of vigour and their usual enthusiasm but the strain of 51/2 hours' playing told. Their ensemble was patchy but Beethoven's music, Davis and the Sinfonietta's naked determination won through.