From the Japanese songs I've listened to, I belive that you do not need to be that careful about the number of kanas in a line. You can always do two things:
- Sing the lyrics kana-by-kana or "the ordinary way". For example, 階段{かいだん} could be sung as either just kai-dan or ka-i-da-n. The former would be 2 syllables and the latter would be 4 syllables.
- Give "unorthodox" furigana to words. I'll illustrate this by an example, which is from Morning Musume's 「時空{とき}を超え 宇宙{そら}を超え」:
時空{とき}を超え 宇宙{そら}を超え 結ばれる頃には
この地球{ほし}は きれいになるかな
Note that 時空, 宇宙 and 地球 are usually pronounced じくう, うちゅう and ちきゅう, respectively, while とき, そら and ほし are respectively 時, 空 and 星. However, the songwriter may assign to words whatever reading they desire, even if it is not a valid reading of the word.
Sometimes this is used for special effect, but sometimes it's probably just to fit the number of syllables, such as this line in AKB48's 「桜の花びらたち」:
その背中に 夢の翼{はね}が 生えてる
I don't really see a reason why 翼 is not pronounced つばさ as it usually is, besides that the syllables would not fit...
Of course, if you are writing enka, you might need to be more careful about the number of syllables. But I suppose you are not into that, so you don't have to get mathematical about the number of syllables.
Is your goal to translate songs or to write your own? If writing your own, I don't have the slightest clue how one would do that until one is fluent enough to ask that of people in Japanese. For translating to Japanese, the problems are similarly difficult.
– virmaior Feb 08 '14 at 13:59I intend to write my own lyrics. I am sort of Intermediate in my Japanese language learning. I have learned that emphasis on certain parts of Japanese vocabulary is taken when it is spoken - I must admit, though, I don't hear the same type of emphasis when the same words are sung. I've heard words sung several different ways in several different songs as well. There are many various ones, so I can't give a specific example at this time.
I suppose that as long as I put melodic emphasis on the same syllables of words as how their spoken, I'll be safe?
– Aurura Feb 09 '14 at 01:05