Ludwig van Beethoven's 33 Variations on a Waltz by Anton Diabelli is one of the great landmarks in piano literature, and it is astonishing how much variety and brilliance Diabelli's charming but trite theme inspired. However, before Beethoven's flashes of genius can be discovered and appreciated, the listener must commit to sit through close to 50 minutes of piano music that is simply overwhelming in its explosive energy and scope. Because of this piece's inherent power, a performer must know when to pull back and when to charge ahead, carefully gauging emotional reactions along the way and taking care not to bludgeon the audience. Daniel-Ben Pienaar is volatile and forceful in this 2011 performance, and for a good part of the piece, he pushes himself, the piano, and anyone else in the vicinity almost to the point of exhaustion. There are variations where he pulls back for reflection, but on the whole, this is an assertive and vigorous reading that requires patience on a first run-through. On a second hearing, however, much that might have passed by unnoticed because of Pienaar's surprising speed, loudness, and aggressiveness becomes easier to follow, and his great energy seems less like an onslaught than an exciting challenge. To close this bracing album, Pienaar includes the Six Bagatelles, Op. 126, which are played with a similar exuberance and dispatch.