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improving music mood classification using lyrics, audio and social tags

improving music mood classification using lyrics, audio and social tags

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Starting from the dataset collected by the procedure described in Section 5.1, i.e., the 8,784<br />

songs with ternary information available, the author identified <strong>mood</strong> categories in this set of<br />

songs <strong>using</strong> similar method described in Section 3.1 <strong>and</strong> then selected songs for each of the<br />

categories. The following subsections describe the process in detail.<br />

5.2.1 Identifying Mood Categories<br />

The <strong>mood</strong> categories identified in Section 3.2 are not directly applicable to labeling the<br />

dataset, because those categories were identified from the most popular <strong>social</strong> <strong>tags</strong> in last.fm.<br />

The songs associated with those most popular <strong>social</strong> <strong>tags</strong> might be very different from the songs<br />

available for this research. On the other h<strong>and</strong>, with the method described in Section 3.1, it is<br />

straightforward <strong>and</strong> efficient to derive <strong>mood</strong> categories that fit a given set of songs. In fact, it is<br />

the strength of this method to be able to efficiently derive <strong>mood</strong> categories for any set of songs<br />

with <strong>social</strong> <strong>tags</strong> available.<br />

The process started from the <strong>social</strong> <strong>tags</strong> applied to the 8,784 songs in the dataset via the<br />

last.fm API. There were 61,849 unique <strong>tags</strong> associated with these songs as of February 2009.<br />

WordNet-Affect was employed to filter out junk <strong>tags</strong> <strong>and</strong> <strong>tags</strong> with little or no affective<br />

meanings. Among the 61,849 unique <strong>tags</strong>, 348 were included in WordNet-Affect. However,<br />

these 348 words were not all <strong>mood</strong>-related in the <strong>music</strong> domain. Human expertise was applied to<br />

clean up these words. Just as in identifying <strong>mood</strong> categories from last.fm <strong>tags</strong>, the same two<br />

human experts identified <strong>and</strong> removed judgmental <strong>tags</strong>, ambiguous <strong>tags</strong> <strong>and</strong> <strong>tags</strong> with <strong>music</strong><br />

meanings that did not involve an affective aspect. As a result of this step, 186 words remained.<br />

58

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