Harmonic Spectral Flux
A variation on spectral flux that is based upon peaks instead of bins. Given
two sets of peaks, calculate the correlation between adjacent peaks. This
should use proper peak tracking, but for now tracks peaks by matching peaks
from the bottom up. Unmatched peaks are discarded. This feature is based upon
Stephan McAdams Spectral Centroid in (McAdams 1999).
McAdams, S. 1999. Perspectives on the contribution of timbre to musical
structure. Computer Music Journal. 23(3):85-102.