Which disco song was played during the film "Saturday Night Fever" but was not on the soundtrack album?

"Disco Duck" is a satirical disco novelty song performed by Rick Dees and His Cast of Idiots. It became a nationwide hit in the United States by September 1976. On the Billboard Hot 100 singles chart, it peaked at number one on October 16, 1976, for one week, held the number-two spot for the following four weeks and remained in the Top 10 for a total of 10 weeks.

"Disco Duck" even made an appearance in the film Saturday Night Fever, in a dance club scene in which a group of senior citizens were learning to dance disco-style. It was also featured in a deleted scene added back to the PG version. As it stands, Dees could have made an even more substantial amount of money from the song. According to Dees, his manager at the time made the unwise decision to deny use of the song on the film's soundtrack because of fears that it would compete with sales of Dees's own album. The Saturday Night Fever soundtrack has now currently sold 40 million copies worldwide, and is the second best-selling soundtrack of all time.