"Back to Basics" was released in August 2006. Aguilera described the record, a double album, as a "throwback" to jazz, blues, and soul music of the 1920s, 1930s, and 1940s that incorporates "a modern twist." She was much inspired by works of such classic blues and soul singers as Otis Redding, Millie Jackson, and Nina Simone during the recording sessions. "Back to Basics" received generally positive reviews from critics, who commented that the retro-oriented production complements Aguilera's vocals. It debuted atop the "Billboard" 200 and has sold 1.7 million copies in the US. At the 49th Annual Grammy Awards in February 2007, Aguilera won Best Female Pop Vocal Performance for "Ain't No Other Man" and performed "It's a Man's Man's Man's World" as a tribute to the late James Brown. "Back to Basics" was succeeded by two international top-ten singles: "Hurt" and "Candyman". Two other singles, "Slow Down Baby" and "Oh Mother", were released exclusively in Australia and Europe, respectively. In support of "Back to Basics", Aguilera embarked on the Back to Basics Tour, which ran from November 2006 to October 2008. With US$48.1 million grossed, the tour was the highest-grossing solo female tour of 2007.