The Russian-British pianist Alexander Melnikov has recorded Shostakovich and a variety of Romantic chamber music with great success. But nothing quite prepares the listener for the controlled power in these performances of three Prokofiev piano sonatas. The Piano Sonata No. 6 in A major, Op. 82, and Piano Sonata No. 8 in B flat major, Op. 84, are among the most modernist works Prokofiev ever wrote. They appeared during World War II and are often thought, with some justification, to reflect that environment.