improving music mood classification using lyrics, audio and social tags

lengths extracted from the song tracks. Almost all of the audio clips were extracted from the
middle of the songs, as the middle part is deemed as most representative for the whole song
(Silla, Kaestner, & Koerich, 2007). There were very few songs whose middle parts contain
significant amounts of silence, in which case the audio clips were extracted from the beginning
of the tracks. In this experiment, the audio length ranged from 5, 10, 15, 30, 45, 60, 90, 120
seconds to the total lengths of the tracks, while the lyric-based system and the hybrid system
always used the complete lyrics. The accuracies averaged across all categories are used for
comparison. Figure 8.2 shows the results.
Figure 8.2 System accuracies with varied audio lengths
The hybrid system outperformed single-source-based systems consistently. With the shortest
audio clips (5 seconds), the hybrid system already performed better than the best performances
of single-source-based systems. Therefore, combining lyric and audio can reduce the length of
audio needed by audio-based systems to achieve better results.
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