Here’s J.S. Bach in his element. Not the distant organist but a fully fledged keyboard virtuoso with a showpiece full of dazzling pyrotechnics, flashy hand-crossings, and quicksilver mood changes. Famous for the cool, understated charm of its opening “Aria,” Bach follows up with a set of 30 variations, positively encyclopaedic in style and soon settling down into a regular pattern: an arresting character piece followed by something virtuosic and then, every third variation, a clever canon. Bach’s variations are not based on the melody of the “Aria” but, unexpectedly, on its bassline and harmonies. This is the key to Hewitt’s performance, which reveals the music from the bottom up. She coaxes, caresses, and charms Bach—more poetry than surface brilliance—bringing a tactile, finger-pleasing joy to the music.