In the live recording of "Notion" on Letterman, Kings of Leon were promoting their fourth studio album, "Only by the Night," which was released in 2008. This album marked a significant turning point for the band, as it propelled them into mainstream success, highlighting tracks like "Sex on Fire" and "Use Somebody" that became global hits. By the time of this performance in 2009, Kings of Leon were experiencing their rise to fame, solidifying their reputation as a prominent rock band of the era. Interesting to note is that "Only by the Night" achieved multi-platinum status and garnered a Grammy Award, underscoring the impact of their live performances during this period. The Letterman performance showcased not just their expanding musicality but also their growing popularity in the American music scene.