Automatic Annotation of Timbre Variation for Musical Instruments Goffredo Haus, Luca A. Ludovico, and Giorgio Presti Universit`a degli Studi di Milano, Dipartimento di Informatica Laboratorio di Informatica Musicale
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Abstract In this work we present a simple timbre-based method to subdivide an audio signal into a stream of grains, each one belonging to a discrete number of timbral classes inferred from the whole signal itself. This is done in the context of a broader project concerning automatic transcription, but it can also serve other purposes. We started developing this algorithm to tackle the task of automatic transcription of a single, monophonic instrument, capable of timbre variations: the khomus – also known in English as the jaw harp and scacciapensieri in Italy – coming from the Tyva Republic and the Sakha Republic in Russian Federation. A MATLAB toolkit performing the operations described in this paper is publicly available to test the effectiveness of the proposed approach.
Correction Synchronization Visualization Annotation
Transcription
Segmentation 1.Preprocessing
Recognition
Comparison
2.Features extraction
3.Clustering and labeling
Input STFT
LPC response
Cepstral coefficients
Envelope and clustered frames
To visualize the results, labels – i.e. MDS scores – are normalized and used as RGB values to color each frame on the base of the cluster it belongs to. Needless to say, labels could be represented through characters or any other symbolic representation instead of colors, but decoding symbols during real-time listening would be less human readable. Moreover, similar frames should have similar colors, and unique sounds should appear as similar for each instance in the performance. Please note that we talk about labels instead of features as they do not convey any musical information, rather they reflect timbre similarities inside the dataset on which MDS is run.
The MATLAB code implementing the algorithm described in this paper is available on GitHub at the following URL: https://goo.gl/aDZWSt This allows a user to replicate the tests performed by the authors, and to experiment with other sound files and parameter settings.
