Lilian Franck and Robert Cibis’ documentary on Stefan Knüpfer, Steinway & Sons’ chief piano tuner in Austria, is as quiet and unassuming as its subject. Subtitled “In Search of the Perfect Sound,” the film tracks the eccentric, witty Knüpfer’s mission to prepare a number of different pianos for a recording of Bach’s unfinished masterpiece The Art of Fugue* by Pierre-Laurent Aimard in the Vienna Konzerthaus. (Lang Lang, Alfred Bendel, Rudolf Buchbinder and David Helfgott also make appearances, though it’s Aimard who occupies the most screen time.) Knüpfer goes to great lengths to manipulate the sound of a traditional Steinway grand (by preparing the strings with various machines, and a tennis ball attached to a length of wood, and by changing the hammer heads and putting extra felt into the body of the piano) so that it variously emulates the tone of an organ and a period clavichord, among other types of keyboard.

In one of the film’s most fascinating moments, he visits a collector to see a 400-year-old clavichord in action. To get one of the pianos to with the acoustics of a certain concert hall, Knüpfer constructs cantilevered arches out of frosted opaque glass that he then places on the piano in order to reflect the sound to the ceiling and into waiting microphones. Knüpfer’s determination to achieve absolute perfection might not sound like something that could be the stuff of an entertaining feature-length documentary, but it is—largely because of his self-effacing charisma and endless neuroses.

Pianomania is now out on DVD through Madman. 46 minutes’ worth of bonus scenes are included as special features.

*Bach’s The Art of Fugue is the subject of another (unrelated) documentary, Desert Fugue.