We spent a long time learning the craft of songwriting, Roger Glover and I, for a few years before we joined Deep Purple. You learn about the percussive value of words, and you learn about rhyme and meter. You learn that you can't transform a poem into a song lyric, mostly because the spoken shape of words is different than the sung shape of words. You wouldn't use the vowel 'U' or the vowel sound 'ooo' for a high note for example, its very difficult.