To what extent do lyrics have to correspond to the tones in tonal languages? I knew they had to, to some extent, but I wanted to find out more about what the rules were. I could hear a strong correspondence in some songs (especially Cantonese) but not others. It seems sometimes tones are completely ignored.
So...I Googled "聲調 歌詞" and found the Wikipedia article 填詞, which said (as of 2013-03-14 09:56)
...which might be BS, since I know Minnan has just as many or more phonemic tones than Cantonese, but I'll take note of it anyway.
Doesn't seem to have any rule about this, as the Wikipedia article described. For example, at "我的愛溢出" one wouldn't expect 出 the high tone character at the lowest note in the little scale there. Another example is 窗臺. It sounds like 闖胎 or something. And this doesn't have to do with tone but stress seems awkward at times the "子" in "院子" is musically stressed. Same with the first-beat-and-fifth-up-to 的 in "也無法將我的" and "像詩裏紛飛的."
But I've also heard that older songs do more to incorporate tones. Let's look at 晴雯歌 by Cao Xueqin, an insert to the novel Dream of the Red Chamber, set to music (with the modern Beijing dialect in mind) by Wang Liping as an insert to the 1987 drama. Starting
Less objectionable, somehow, but somehow I still don't see any real intent to use the tones. Sure, at the end he didn't put 天 on the A and instead saved it for the higher D, but at the beginning there's a 比 on a higher note than 心 and 天. There's "靈巧," with the 巧 on the highest note in the range.
Without exception, the endpoints of the tones (and tone letters) correspond with the notes. A few parts sound close to how one would speak it, such as "也是我運氣." Ornaments might play a role in this, as one can often hear a lower grace note before characters with rising tones. The result is highly intelligible lyrics. This song isn't special, AFAIK, as Cantonese lyrics are usually written in such a manner. So I guess the Wikipedia article is kind of right although some details might be messed up.