The stylus, developed by Philippe Robert and colleagues at the Federal Institute of Technology in Lausanne, relies on a single optical fibre a thousand times lighter than a conventional diamond needle. It can now play ageing 78 rpm discs and cylinders that were too fragile or damaged to play.
Some cylinders were so delicate they could only be played once. The weight of the hard needle had also worn away the groove because the discs were too soft.
But Robert told New Scientist: "We have played many times soft wax discs which can usually only be played once or twice. We have listened to speeches by wartime leaders such as Churchill, Roosevelt and Hitler. We were particularly charmed by a broadcast by the then Princess Elizabeth made for the BBC on her 14th birthday."