Of the twelve composers in our series ''At the piano'', Franz Schubert was undoubtedly the least at home at the piano - but nevertheless what masterpieces he left us for this instrument! There is hardly any pianist who is not immediately captivated by the cheerful yet melancholy atmosphere of Schubert's impromptus and Moments musicaux. Even the simple pieces by Schubert at the beginning of this volume have surprising twists in store that afford them a profundity of their own. Nor are his dances mere ''entertainment''. No matter how charming they may seem on the surface, there is always a wistful tone in his waltzes and landler. This seems to reflect the gravely ill composer's presentiment of his own death.