Musical recordings, when performed by non-proficient (amateur) performers, include two types of tempo fluctuations–intended “tempo curves” and non-intended “mis-played components”–due to poor control of instruments. In this study, we propose a method for estimating intended tempo fluctuations, called “true tempo curves,” from mis-played recordings. We also propose an automatic audio signal modification that can adjust the signal by time-scale modification with an estimated true tempo curve to remove the mis-played component. Onset timings are detected by an onset detection method based on the human auditory system. The true tempo curve is estimated by polynomial regression analysis using detected onset timings and score information. The power spectrograms of the observed musical signals are adjusted using the true tempo curve. A subjective evaluation was performed to test the closeness of the rhythm, and it was observed that the mean opinion score values of the adjusted sounds were higher than those of the original recorded sound, and significant differences were observed for all tested instruments.

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