Doo-wop songs are a genre of music that originated in the 1940s and 1950s. They are characterized by their use of vocal harmony, simple chord progressions, and often nonsense syllables. The term 'doo-wop' is derived from the sound made by the vocalists. OLDIES is an umbrella term used to describe popular music from the 1950s and 1960s. It is often used interchangeably with doo-wop songs, as many of the most popular OLDIES songs are doo-wop songs.