The early movie musicals of the 1950s used rehashed songs from earlier movies and stage plays. This was particularly true with movies that featured the music of established composers such as Irving Berlin or the Gershwins. Often, the songs featured in these movies had been popular hits in earlier decades (for example, "I've Got Rhythm" in "An American in Paris"). Adaptations of Broadway musicals rarely saw changes in the songs from the original Broadway productions (this changed in the 1960s).
This section of the website lists the songs from each movie, along with information on the songs that were also popular hits.