The issue of tuning has been a live one ever since Greek mathematician and philosopher Pythagoras was pinching strings and scratching his head over harmonic discrepancies 2,500 years ago. For a keyboard instrument such as the piano with its multiple strings, until the system of Well Temperament was popularised in the early 18th century, instruments would only really sound good tuned to a certain key. Thanks to the Well-Tempered method of tuning though, and yes, Bach knew what he was doing when he wrote that collection of pieces in all 24 keys to be played on the same instrument, the pianist now has freedom to transpose freely across the keyboard. Yet, piano tuning is a highly nuanced art, affecting the tone and colour of an instrument. With razor-sharp hearing and an ability to creatively play with the compromises necessary to tune a piano, the piano tuner still plays a key role in preparing an instrument for performance. Featuring Marcus du Sautoy, Angela Hewitt and Richard Foster.