POLYPHONIC MUSIC TRANSCRIPTION USING NON NEGATIVE MATRIX FACTORIZATION
This paper describes a method to automatically transcribe polyphonic music using non negative matrix factorization (NMF) Previous works have shown that NMF performs convincingly in characterizing the note layout as well as the spectral distribution of each note. I am going to explore the method in the context of four part harmonies on piano. First, the spectrogram of the input audio file is calculated using short time Fourier transform. Then, the spectrogram as a matrix is decomposed into a product of the spectral template and the activation matrix. Next, an energy based method is used to detect the onsets of each note. Finally, the midi number of the notes are obtained from the fundamental mental frequencies in each column of the spectral template.