"Chroma and Bass Chromagram" output will be different from the individual 12-dim. Note that normalisation implies that the joint 24-dim. If the setting is not 'none', then each chroma frame separately is divided by the chosen vector norm. * chroma normalisation (none, maximum norm, L1 norm, L2 norm default: none): determines whether or how the chromagrams are normalised. Their harmonic amplitude follows a geometrically decreasing pattern, in which the i-th harmonic has an amplitude of ^, where "^" means "to the power of". * spectral shape (0.5 - 0.9 default: 0.7): the shape of the notes in the NNLS dictionary. For values other than 0.0 the log-freq spectral bins are divided by ^, where "^" means "to the power of". * spectral whitening (0.0 - 1.0 default: 1.0): determines how much the log-frequency spectrum is whitened. Local tuning is only advisable when the tuning is likely to change over the audio, for example in podcasts, or in a cappella singing. * tuning mode (global or local default: global): local uses a local average for tuning, global uses all audio frames.
A value of 0 means that no bins will be changed. All bins below the first bin whose cumulative energy exceeds the quantile x will be set to 0. * spectral roll on spectral roll on (0 % - 5 % default: 0 %): consider the cumulative energy spectrum (from low to high frequencies). * use approximate transcription (NNLS) (on or off default: on): toggle between NNLS approximate transcription and linear spectral mapping. The default settings (in brackets, below) are those used for Matthias Mauch's 2010 MIREX submissions. The resulting chroma frames can be normalised by (dividing by) their norm (L1, L2 and maximum norm available).
To get the chroma, this semitone spectrum is multiplied (element-wise) with the desired profile (chroma or bass chroma) and then mapped to 12 bins. The output of the NNLS approximate transcription is semitone-spaced. The processed log-frequency spectrum is then used as an input for NNLS approximate transcription (using a dictionary of harmonic notes with geometrically decaying harmonics magnitudes). * running standardisation: subtraction of the running mean, division by the running standard deviation. ) corresponds to a semitone, even if the tuning of the piece deviates from 440 Hz standard pitch. * tuning, after which each centre bin (i.e. On this representation, two processing steps are performed: The spectrum is transformed to a log-frequency spectrum (constant-Q) with three bins per semitone. The plugin was originally developed to extract treble and bass chromagrams for subsequent use in chord extraction methods. NNLS Chroma analyses a single channel of audio using frame-wise spectral input from the Vamp host. System identifier – vamp:nnls-chroma:nnls-chroma
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