The album features some of the group's biggest hits from its heyday in the 1990s as well as a number of previously unreleased tracks and will not hit music retailers until next week (begs04Oct10).
Cornell admits Soundgarden agreed to the rare move in a bid to reach a new generation of rock fans, reports the Associated Press.
He says, "In the obvious way, it's going to reach a certain amount of younger people that either may or may not know about Soundgarden.
"No matter what, I feel like releasing it this way is going to reach a lot of people who have not heard our music or have not heard a lot of it."
And he's been intrigued by the Guitar Hero franchise, which allows gamers to rock out with their icons on a guitar-shaped controller, since its inception in 2005: "I thought about doing this ever since I've heard about the game and what it is. I think the musical arrangements lend itself so well to what the video game is."