Explicit beat structure modeling for non-negative matrix factorization-based multipitch analysis

This paper proposes model-based non-negative matrix factorization (NMF) for estimating basis spectra and activations, detecting note onsets and offsets, and determining beat locations, simultaneously. Multipitch analysis is a process of detecting the pitch and onset of each note from a musical signal. Conventional NMF-based approaches often lead to unsatisfactory results very possibly due to the lack of musically meaningful constraints. As music is highly structured in terms of the temporal regularity underlying the onset occurrences of notes, we use this rhythmic structure to constrain NMF by parametrically modeling each note activation with a Gaussian mixture and derive an algorithm for iteratively updating model parameters. It is experimentally shown that the proposed model outperforms the standard NMF algorithms as regards onset detection rate.