"Music lovers expect extraordinary feats from us pianists," says Anton Kuerti . "We're expected to perform physical motions of extreme accuracy, subtlety and speed, and do them perfectly, very near the border of the impossible." In order to facilitate such virtuosity, however, it is first necessary to tune one's instrument. The journey from the mundane to the sublime is exquisitely captured in director David Acomba's intimate portrait of this celebrated musician. As Kuerti tinkers and mutters over his piano, the work of genius is revealed to be just that, work. With his tool kit in hand, Kuerti sets about applying Teflon, tightening loose hammers and softening harsh strings, making dozens of minute adjustments. Like a race car, the piano is an unforgiving performance machine. "Every new instrument provides a recipe for disaster," he says. In order to attain the enormous dynamic range and variance of tone and colour required, every part of the piano must be perfectly in balance. Before a public performance, comes this solitary act, a sacred rite enacted in a dark and empty hall.