Final answer:
The musical element described with the phrase "two-part AB form" is the verse-chorus form, where two sections of music (the verse and chorus) are alternated.
Step-by-step explanation:
The musical element described with the phrase "two-part AB form" is the verse-chorus form. In this form, two sections of music are alternated: the verse (A) and the chorus (B). The verse tells a story or develops a theme, while the chorus provides a catchy and repetitive section that serves as the main hook of the song.
For example, many popular songs follow this structure, such as "Hey Jude" by The Beatles, where the verse sections tell a narrative and the chorus section repeats the famous "na na na" melody.