Schubert wrote his B-flat Piano Sonata in the last months of his life in 1828, and for many years it languished in the shadow of Beethoven’s towering output in the same form. Nowadays, its genius is recognized and has attracted the greatest pianists to scale its heights. Khatia Buniatishvili goes for a softer focus than is often the case, and her approach makes for a refreshing change from the usual assault. Her piano sings and the Scherzo is almost Mendelssohnian in its fleetness of foot. The 4 Impromptus, too, are played with delicacy and great tenderness.