Time Out says
There's achieving the pitch-perfect tone, and then there's Steinway & Sons piano technician Stefan Knpfer's goal: a symbiotic union between musician and instrument. From finding pianist Lang Lang a bench that won't creak to using something resembling a nail gun with a tennis ball attached to break in new strings, Knpfer serves a wide swath of artists down to the last timbre; in preparing to record Bach's The Art of Fugue, Pierre-Laurent Amard spent a year working with him to devise separate sounds for each component piece. When sitting through this detail-heavy documentary, nonaficionados may feel like they're watching paint dry, albeit in the company of an artist who savors each and every shade.
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Watch the trailer