I’ve been asked a number of times: if Mandarin Chinese is a tonal language, what happens when you sing in Mandarin? Well, the answer is the melody takes over and the tones are ignored. Pretty simple.
However, it may not quite end there. I recently discovered a paper called “Tone and Melody in Cantonese” which asserts that Cantonese tones are set to music in a somewhat different way:
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.
Here’s a graphical representation of Cantonese tones, with and without music:
And here’s an example of Mandarin:
I can’t say I’m fully convinced by the pitch contour graphic that the Cantonese songs “take the lexical tones into consideration,” but it’s an interesting argument. This would suggest that studying songs would be more beneficial to acquisition of tones for the student of Cantonese than for the student of Mandarin.
If you’re interested in this kind of thing, Professor Marjorie K. M. Chan has lots of articles available on her website’s Publications page.