Formally, the Trio has a classical shape. The first movement is in sonata form, with an expanded recapitulation. The second movement combines a forceful Presto and an eerie, unworldly trio episode, both recapitulated, and 'squeezed together' in a short coda. The third movement is a rather free Adagio, with the three players used more as soloists than elsewhere in the work. The finale is a kind of rondo with variations, in which all the subsidiary...