See Serj Tankian Join Tool for Stunning Performance of "Sober" in 2007 | Revolver

See Serj Tankian Join Tool for Stunning Performance of "Sober" in 2007

System of a Down singer helped take 'Undertow' single next level

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In January 2007, Tool were at Princes Park in Melbourne, Australia, playing the Big Day Out festival, and true to the event's name, they went big and pulled out all the stops. The prog-metal juggernaut's hour-and-20-minute set opened with "Stinkfist" and closed with "├ćnema," and offered up choice cuts, including "Swamp Song, "Forty Six & 2" and "The Pot," in between. "I'm a little winded," Maynard James Keenan joked dryly at one point. "Would you mind finishing the rest of the set for me? I've got some hotel porn to get back to ... Time's a wastin'."

While the crowd did, of course, help out mightily, singing along to virtually every word, Keenan's most notable assist came from none other than Serj Tankian. The System of a Down frontman stepped out onstage around the 3:30 mark of Tool's centerpiece performance of Undertow's "Sober," delivering an operatic vocal solo that took the song into a whole other realm of mind-bending awesomeness. Watch fan-shot footage above, and check out video of the band's full set below.