For Stefan Knüpfer, achieving the perfect tone is all-consuming. Unsurprising when your clients include Pierre-Laurent Aimard, Lang Lang and Alfred Brendel. For Knüpfer is Steinway’s Master Tuner in Vienna, and as such, is responsible for maintaining Steinway’s reputation for superior sound – and where appropriate altering that sound to suit the exacting requirements of the world’s leading pianists.

The documentary Pianomania, which opens in selected cinemas on Friday, charts a year in the world of Knüpfer. Central to the story are his efforts to achieve multiple tones – through some highly inventive means – for Aimard’s 2008 DG recording of Bach’s Art of Fugue. It’s a long, difficult and at times painful process – witness Knüpfer’s crushing disappointment when his specially designed panels to give the piano a more organ-like sound are abandoned during the recording sessions - yet one that clearly gives much joy and satisfaction. When Aimard finally turns to the Master Tuner with the words “Stefan, I have always dreamt of this sound,” one might well shed a tear.

Directors Robert Cibis and Lilian Franck have taken great care to ensure audiences can appreciate the fine alterations in tonal quality. The film was shot in high definition and in Dolby surround sound on 90 separate tracks, a process which allows the audience to experience in some part Knüpfer’s superhuman aural abilities – at least for the duration of the film.  

Pivotal to Pianomania, though, is the quiet charm and enthusiasm of its protagonist. Clearly a great talent in his own right, Knüpfer is happy to remain behind the scenes – as he puts it, “to disappear offstage when the audience enters”. Musician, craftsman, scientist and wry observer – “pianists are mostly dissatisfied” – his passion alone could easily sell the subject matter. But the chance, too, to see leading pianists behind the scenes is not to be missed.

For information on cinemas showing Pianomania visit www.more2screen.com