Abstract
In this paper, a piano chords detector based on parallel interference cancellation (PIC) is presented. The proposed system makes use of the novel idea of modeling a segment ofmusic as a third generation mobile communications signal, specifically, as a CDMA (Code Division Multiple Access) signal. The proposed model considers each piano note as a CDMA user in which the spreading code is replaced by a representative note pattern. The lack of orthogonality between the note patterns willmake necessary to design a specific thresholding matrix to decide whether the PIC outputs correspond to the actual notes composing the chord or not. An additional stage that performs an octave test and a fifth test has been included that improves the error rate in the detection of these intervals that are specially difficult to detect. The proposed system attains very good results in both the detection of the notes that compose a chord and the estimation of the polyphony number.
Highlights
In this paper, we deal with a main stage of automatic music transcription systems [1]
The evaluation of the performance of the parallel interference cancellation (PIC) detector for piano chords described in this paper and the comparison of the result versus a selected technique in [4] have been done using samples taken from different sources
The model proposed considers each piano note as a code division multiple access (CDMA) user in which the spreading code is replaced by a representative note pattern defined in the frequency domain
Summary
We deal with a main stage of automatic music transcription systems [1]. In the context of musical signals, regarding the problem of detection of the notes that compose a musical chord, the orthogonality condition between the spectral patterns of the different notes cannot be achieved. This is due to the harmonic relations that exist between the notes of the equal-tempered musical scale typically used in Western music, specially between octaves and fifths (despite inharmonicity and stretched tuning [16]). In order to perform the detection of the notes that sound in a certain segment or window of a musical audio signal, we have considered the CDMA detection technique called Parallel Interference Cancellation (PIC).
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