Final answer:
John Kander and Fred Ebb composed and wrote the lyrics for Cabaret and Chicago, both considered influential works within the concept musical genre.
Step-by-step explanation:
The composer/lyricist duo that wrote Cabaret and Chicago within the concept musical genre were John Kander (composer) and Fred Ebb (lyricist). In the era that these musicals were created, America was undergoing massive social and cultural changes. The duo's work represented a new wave of musical theatre that was socially conscious and pushed against the norms of traditional, romantic musical narratives.
Their musicals, particularly Cabaret, which was set in the Weimar Republic's volatile times, and Chicago, which satirized the concept of the celebrity criminal, were both successful in challenging audiences and introducing innovative themes and structures to the genre of concept musicals.