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OFAI-TR-2005-16 ( 138kB PDF file)

Live Tracking of Musical Performances using On-Line Time Warping

Simon Dixon

Dynamic time warping finds the optimal alignment of two time series, but it is not suitable for on-line applications because it requires complete knowledge of both series before the alignment can be computed. Further, the quadratic time and space requirements are limiting factors even for off-line systems. We present a novel on-line time warping algorithm which has linear time and space costs, and performs incremental alignment of two series as one is received in real time. This algorithm is applied to the alignment of audio signals in order to follow musical performances of arbitrary length. Each frame of audio is represented by a positive spectral difference vector, emphasising note onsets. The system was tested on various test sets, including recordings of 22 pianists playing music by Chopin, where the average alignment error was 59ms (median 20ms). We demonstrate one application of the system: the analysis and visualisation of musical expression in real time.

Keywords: Audio alignment, Music performance analysis, Dynamic time warping

Citation: Proceedings of the 8th International Conference on Digital Audio Effects (DAFx05), Madrid, Spain, September 2005, pp 92-97.