Final answer:
The genre of popular music most similar to a Baroque lament is the Blues, which shares the same themes of melancholy and emotional depth, and features a repeating harmony structure with its twelve-bar blues progression.
Step-by-step explanation:
The genre of popular music, similar in mood and intent to a Baroque lament and known for its repeating harmony, is the Blues. Originating from the deep emotional narratives of African American spirituals, work songs, and folk ballads, Blues music encapsulates themes of suffering, heartache, and a quest for redemption, echoing the melancholic ethos of the classical laments. The Blues is characterized by its chord progressions, often based around the twelve-bar blues structure, its soulful melodies, and its expressive, often sorrowful lyrics which share a kindred spirit with the lament in Baroque music.