Simple drums separation with NMF

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This script illustrates the use of NMF for the extraction of the drums section in polyphonic music. It makes use of the NMF and Signal classes that are available in Mathworks file exchange.

The main lines of the technique are:
* compute onsets for different frequency bands.
* model the whole signal as an NMF, with the H of the components corresponding to the drums being initialized with the onsets
* perform a filtering of the signal

This code should work reasonably OK for small files (approx 30s). When using this script for research purpose, please be so kind as to provide the corresponding reference:

@ARTICLE{LiutkusGPSS,
author={Liutkus, A. and Badeau, R. and Richard, G.},
journal={Signal Processing, IEEE Transactions on},
title={Gaussian Processes for Underdetermined Source Separation},
year={2011},
month={july },
volume={59},
number={7},
pages={3155 -3167},
doi={10.1109/TSP.2011.2119315},
ISSN={1053-587X},}