matching-methods · dannenberg2006-score-alignment-accompaniment

Readers are likely familiar with the Viterbi Algorithm, which uses dynamic programming to solve this problem without actually enumerating every path. [...] Unfortunately, multi-pitch estimation is unreliable and still an active research area, so today's score-alignment systems use representations based on the distributions of frequencies in the signal, also known as the spectrum. [...] A popular technique for comparing spectra from scores to spectra in music audio is to reduce the detailed spectrum to a 12-element chroma vector [...]. The earliest computer accompaniment systems matched note sequences rather than spectral data, reducing data rates and computation. [...] Hidden Markov models have been explored for score following, allowing systems to be trained using rehearsals to follow more accurately and to respond with less latency. [...] Another approach avoids the problem of discrete states by representing score position as a continuous probability density function.