At first, this was going to be sung by a jingle singer named Kasey Cisyk, and she recorded the original version that was used in the film (the film's director Joseph Brooks was a jingle writer for a while, and was impressed with how Cisyk sang his tunes). For over a year, no movie studio would release the film and no record company would release the song. When the movie finally got picked up, it was time to record the song as a single, and Brooks went with Debby Boone instead of Cisyk, who also plays a bridesmaid in the film. Boone had very little recording experience, but was the daughter of Pat Boone, a very popular singer in the '50s with a loyal and very religious fan base.
Boone's vocal was done over the same instrumentation, and Brooks had her do it exactly like Cisyk's; in a number of interviews, she described him as being so mean to her that she was reduced to tears. Only a very discerning ear can tell the difference between Boone's version and the one used in the movie, which apparently was the goal. Why Brooks didn't use Cisyk's recording as the single is unclear, but there was apparently a falling out of some kind, and Cisyk, who died of breast cancer in 1998 at age 44, never told her side of the story, possibly restrained by legal action she took against Brooks. According to Cisyk's husband Ed Rakowicz
, Brooks was retaliating against her because she rebuffed his advances.
Cisyk never became a recording star, but was heard on many popular commercials, including the "Have You Driven a Ford Lately?" campaign.