The restoration of pitch variation defects in gramophone recordings

A new algorithm is presented for the identification and restoration of time-varying pitch defects in audio signals. The problem is commonly encountered as `wow´ in gramophone disc and magnetic tape recordings where motor speed variations or eccentricity in the recording process are significant. The algorithm operates in two stages, the first of which trades tonal components in musical signals to generate a single pitch variation curve, and the second stage which performs restoration as a time-varying resampling operation. Results are presented from both artificially degraded sources and real sources