Some song lyrics in the official lyric book that accompanies the CD is sung as another word. Usually, the way it is sung is given as a furigana on the kanji:
(pardon the quality I took it using iPhone)
(ひとりじゃない by DEEN)
(Pray by Every Little Thing)
I wonder why write the word "希望" in the first place. Why not just print word "ゆめ" since you won’t hear the word "きぼう" in the song anyway? Is there a cultural/artistic reason for it?
EDIT by Scratch---Cat: A really significant example in an extremely well-known song (senbonzakura)