1. A method of extracting an audio signal from a mechanical recording having a modulated groove on a surface, wherein said groove is formed by a modulated curvilinear longitudinal profile substantially orthogonal to a plurality of sequential transverse profiles from beginning to end of the groove, said longitudinal profile at each point in the transverse profile substantially tangent to said surface, each transverse section comprising two side surfaces and a bottom surface distanced from said surface, comprising: i) profiling said mechanical recording to form a metrological data set comprising metrological data; and ii) processing said metrological data set by obtaining transverse profiles of said longitudinal profile representative of the modulated groove in three dimensions; and iii) further processing said metrological data set to reconstitute said audio signal defined by variations in the modulation of said modulated groove.