improving music mood classification using lyrics, audio and social tags

systems and the audio-only system was statistically significant, but the difference between
hybrid systems and the lyric-only system was not statistically significant.
Figure 7.3 shows the system accuracies across individual mood categories for the BEST
lyric feature set where the categories are in descending order of the number of songs in each
category.
Figure 7.3 System accuracies across individual categories for the BEST lyric feature set
Figure 7.3 reveals that system performances become more erratic and unstable after the
category “cheerful.” Those categories to the right of “cheerful” have fewer than 142 positive
examples. This suggests that the systems are vulnerable to the data scarcity problem. For some of
the smaller categories, system performances were even lower than baseline performance (50%
for binary classification). This is a somewhat expected result as the lengths of the feature vectors
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