Let It Go

In April 2006, McGraw and Hill began their 73-concert 55-city Soul2Soul II Tour, again to strong commercial acceptance. The tour grossed roughly $89 million and sold approximately 1.1 million tickets, making it the top grossing tour in the history of country music. It was also named "Major Tour of the Year" by the prestigious Pollstar Magazine, beating out such heavyweights as Madonna and the Rolling Stones. In a special gesture, the couple donated all of the profits from their performance in New Orleans to Hurricane Katrina relief.
McGraw, along with Kenny Chesney, contributed to a version of Tracy Lawrence's song "Find Out Who Your Friends Are", which can be found on Lawrence's album For the Love. Although the official single version features only Lawrence's vocals, many stations have opted to play the version with McGraw and Chesney instead.
McGraw released his eleventh studio album, Let It Go, on March 27, 2007. The album's first single, "Last Dollar (Fly Away)", peaked at number one on the Hot Country Songs chart. This marked McGraw's first No. 1 single since "Back When" in late-2004. The album debuted at No. 1 on both the Billboard 200 and Top Country Album charts, marking his fourth No. 1 album on the 200 charts and his ninth overall. His daughters can be heard singing the chorus during the last few seconds of the song on the video.
During the Academy of Country Music awards show on May 21, 2007, McGraw performed a song titled "If You're Reading This", which he co-wrote with The Warren Brothers. Several radio stations began to play the live recording of the song; as a result, it entered the U.S. Billboard Hot Country Songs chart at No. 35.
McGraw also produced the debut album of country music duo Halfway to Hazard. The duo's first single, "Daisy", peaked at No. 39 on the country charts in the summer of 2007.
In the summer of 2007, McGraw and Hill toured together once again in the Soul2Soul 2007 tour.
In the January 18, 2008 edition of the USA Today newspaper, McGraw was stated to be featured on the Def Leppard album Songs from the Sparkle Lounge, having also co-written the first single, "Nine Lives", with Def Leppard band members Joe Elliott, Phil Collen, and Rick Savage. The unusual pairing goes back to 2006 when McGraw joined Def Leppard onstage for the song "Pour Some Sugar On Me", and then collaborated on the song "Nine Lives" afterward. The album was released on April 25, 2008.
At the 2007 50th Annual Grammy Awards, McGraw received 5 nominations including Best Country Album (for Let It Go, Best Country Song (both for "If You're Reading This" and "I Need You"), Best Country Collaboration with Vocals (with "I Need You"), and Best Male Country Vocal Performance (with "If You're Reading This").
In May 2008, he hit the road with the Live Your Voice tour. The mainly-outdoor arena concert tour was his first solo outing in nearly three years. Also in May 2008, he debuted a new song off of his follow-up to Let It Go at the Stagecoach Music Festival in Indio, California.
In July 2008, the album's sixth single and its title track, "Let It Go", was released to country radio. Following that, a seventh single, "Nothin' to Die For", entered the Country charts at No. 57 in late December. McGraw released his third greatest-hits package, Greatest Hits 3 on October 7, 2008. The album features 12 tracks. McGraw was set to debut a new song on the 2009 ACM Awards, but then cancelled his performance; he was replaced by Blake Shelton, who sang "She Wouldn't Be Gone".