Explanation: Backing vocals can be simple and can be complicated. There will be sections where backing vocals simply harmonize with the melody, singing the same exact words and phrasing, just on different notes. For those sections, all you need to know is the singers' ranges and the appropriate chords.
Counterpoint parts and turnarounds add to the arrangement, but introduce the element of lyrics into the mix. Sometimes you'll need to add a couple of words, or subtract them, so that the whole performance makes sense. A bad example of this is in the Celine Dion recording of the Titanic song. She keeps singing about how the heart goes on, while the choir at one point sings " why does the heart go on." They needed an extra syllable, and added a word that just does not make sense to me. But it shows what one has to think of when writing backing vocals that do turnarounds at the end of phrases.
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