MelBands (when fed with the output of Spectrum) seems to work fine for low numbers of bands, e.g. 24 or 40. But if we increase this number to e.g. 128 or 256, it seems to (mistakenly) always return 0 for specific band numbers.

For instance when setting numberBands = 256, regardless of which audio file I analyze I get 0 in the following bands:

array([[ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16,
        17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 36,
        37, 39, 40, 41, 42, 44, 45, 46, 47, 49, 51, 53, 54, 56, 58, 60, 62,
        64, 67, 69, 71, 74, 79, 82]])

Here are some example spectrograms (of the log-melbands, ignore the y-axis labels):