Some of Franz Schubert’s piano sonatas suffer from longueurs, but the final two — in A major (D. 959) and B-flat major (D. 960) — are perfect works of genius written shortly before his death. The current catalog offers readings of the B-flat Sonata by about 120 pianists and approximately two-thirds that number for the A-major. That is no reason to be less than jubilant that Krystian Zimerman finally committed to recording his interpretations in early 2016, shortly after his fifty-ninth birthday. Nearly two years later, the disc has finally reached the shelves. One is instantly struck by the piano’s sound. Zimerman, who serves as his own technician, likes to customize pianos for individual pieces or programs. Here he has positioned the hammers to strike an unaccustomed place on the strings and has lightened the action. The resulting tone is simultaneously resonant and translucent, a winning compromise between modern and historical aesthetics. Recording engineer Rainer Maillard captured the sound magically during five days of takes in a Japanese concert hall, from a relatively close perspective but without a trace of harshness. Zimerman’s interpretations rank with the finest — securely paced but pausing selectively over details, underscoring Schubert’s mercurial moods without sounding gimmicky. The A-major turns terrifying in its slow movement but, by the end, seems consoling in its optimism. Energy never flags in the B-flat, where profound mystery proves perpetually enriching.