Given rapt attention and care in the framing, there is no more engrossing subject than man at work. The proof, yet again, is in director Ben Niles’ chronicle of the production of a single Steinway concert grand—a nine-foot beast that requires a plank the length of an anaconda, a year of assembly, and a small army of blue-collar technicians whose skills are as minutely focused and compartmentalized as a safecracker’s. Niles gathers testimonials from a variety of pianists, from classical (Hèléne Grimaud, the infectiously effusive Chinese prodigy Lang Lang) to jazz (Harry Connick Jr., Hank Jones, Marcus Roberts), to describe and demonstrate the variances of sound inimical to each Steinway, among the last of the hand-crafted pianos. But they’re distractions from the drama in Steinway’s Queens factory, where a single slip of a “pizza wheel” wire stretcher or an imbalance of a few thousandths of an inch could ruin a $25,000 instrument. Niles and cinematographer Ben Wolf scrutinize each step as if it were Rififi’s climactic heist, offering moments of fixated strangeness and wonder—as when a burly Croatian “bellyman” named Ante Glavan installs perfect rows of teensy little notches in the bridge, using swift, unhesitant repetition that seems more magical than robotic. The movie may sell the Steinway supremacy a bit insistently—no wonder a film link turns up on the manufacturer’s website—but as a study of stubborn artisanal tradition in the ProTools age, Note By Note is a stirring symphony of specialized labor.