Yuen Ren Chao:
In the matter of chanting poetry, you follow more or less the tonal patterns of the dialect in which you're chanting. But in singing, there is more freedom, although I think there are articles and books even that have been written on the matching of tones with melody. But in modern colloquial verse, one usually doesn't pay too much attention to them.
I've been more or less influenced by the classical tradition of singing the first two Mandarin tones — the so-called even tones — on a low pitch or a descending pitch, whereas the other tones would have either shorter or higher tones. I've followed the Mandarin tones only in a few cases in playful, humorous songs. I haven't followed the Mandarin tones when I compose tunes to the words. I've always been rather conservative in that respect.
In Chinese linguist, phonologist, composer and author, Yuen Ren Chao, with an Introduction by Mary Haas; an Interview Conducted by Rosemary Levenson, (The Bancroft Library University of California, Berkeley; China Scholars Series), 1974: 160–61. On line at the California Digital Library (accessed 20131102).