Originally written by Ford and Fox, "Heartbeat" was conceived as a mock love song to Joey Ramone and was initially intended to feature Fox on lead vocals. Because Currie had already lost a significant number of lead vocals to Jett by the time it was recorded, Fowley decided to have Fox and Currie sing the lead vocals together in an effort to appease Currie, but Fox recalled that "Cherie's voice and mine didn't blend well at all" and they gave up trying to record together. Without Fox's knowledge or approval, Currie and Fowley then rewrote the lyrics to be about David Bowie and recorded the vocals without Fox.
The song "Heartbeat" was initially written with Fox in mind, but the lyrics were rewritten and recorded without his knowledge or approval after Currie lost several lead vocalists.