The biggest classic rock stories of May 2017 included some sad losses, the kick-offs of major tours and a fun surprise collaboration. Check them out below.

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Gregg Allman Dies

Gregg Allman, who had led the Allman Brothers Band for more than 40 years following his brother Duane's tragic death, died at 69 on May 27. The band had called it quits in 2014 after a series of celebrated final shows, but Allman had continued working until the end. His final solo album, Southern Blood, was released posthumously in September as several shows were planned to celebrate his life. Allman has also been nominated for a Grammy Award for Best Americana Album, while one of its songs, "My Only True Friend," has been nominated for Best Americana Roots Song. On losing their friend, his longtime collaborators and pals reflected on Allman's work and friendship.

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Chris Cornell Dies

At the age of 52, Soundgarden and Audioslave frontman Chris Cornell died on May 18 when he hanged himself in a Detroit hotel room. Cornell had also played with future members of Pearl Jam in Temple of the Dog, and put a number of solo records. His unexpected death sent a shockwave through the music community, and tributes began pouring in from all sides. Aerosmith dedicated "Dream On" to him, and Guns N' Roses covered "Black Hole Sun." Serj Tankian joined Prophets of Rage for a cover of "Like a Stone," and the Head and the Heart covered "Hunger Strike." He was openly mourned by fellow musicians and friends like his longtime pal Eddie Vedder and hometown friends from Heart. Of course, all of his former bandmates penned tributes to their friend.

Cornell has been posthumously nominated for a Grammy for his song "The Promise," which was written for the film of the same name about the Armenian Genocide, and received the inaugural Promise Award from the Los Angeles Committee of Human Rights.

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Roger Waters Kicks Off Tour

On May 26, Roger Waters kicked off his North American Us + Them tour, ahead of the June release for Is This the Life We Really Want?, his first album of new material in 25 years. It had been more than 15 years since he'd toured without playing an entire Pink Floyd record, with inspiration for the new album coming, in part, from the election of President Donald Trump. Throughout the tour, Rogers has been outspoken in his criticism of the Trump administration, and his desire for the man to be removed from office. He also approved an Animals-inspired art installation comprising four giant gold-colored, helium-filled pigs to be strategically placed in a way that blocks out Trump's name from Chicago's Trump Tower.

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Metallica Kicks Off Tour

On May 11, Metallica kicked off their North American WorldWired tour, following the release of their Hardwired... to Self-DestructThe album marked their first studio release in eight years, and the band hadn't packed in such an extensive schedule since the World Magnetic Tour six years earlier. The tour helped them top the list of highest-earning rock artists in 2017.

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Brian Johnson Returns to the Stage

Former AC/DC singer Brian Johnson left the band's 2016 tour after doctors warned that his continued performance with the band could lead to permanent hearing loss. But on May 14, he joined Bad Company frontman Paul Rodgers solo tour for an encore performance of Barrett Strong's "Money." They even got a bit more help from Led Zeppelin's Robert Plant. The special collaboration took place midway through Rodgers' Free Spirit solo tour, which focused on the work of his first band, Free. Plant had recently recorded an episode of Johnson's TV show A Life on the Road, which is likely how the threesome got together.