Interestingly, Cantonese songs tend to preserve tone better than songs sung in Mandarin. The paper "Tone and Melody in Cantonese" by Marjorie K.M. Chan [1] mentions the following:
> For Chinese, modern songs in Mandarin and Cantonese exhibit very different behaviour with respect to the extent to which the melodies affect the lexical tones. In modern Mandarin songs, the melodies dominate, so that the original tones on the lyrics seem to be completely ignored. In Cantonese songs, however, the melodies typically take the lexical tones into consideration and attempt to preserve their pitch contours and relative pitch heights.
> For Chinese, modern songs in Mandarin and Cantonese exhibit very different behaviour with respect to the extent to which the melodies affect the lexical tones. In modern Mandarin songs, the melodies dominate, so that the original tones on the lyrics seem to be completely ignored. In Cantonese songs, however, the melodies typically take the lexical tones into consideration and attempt to preserve their pitch contours and relative pitch heights.
[1] https://journals.linguisticsociety.org/proceedings/index.php...