Soundgarden frontman Chris Cornell, on writing the lead track for Machine Gun Preacher and making an appearance in Cameron Crowe’s Pearl Jam Twenty.

Chris Cornell, the godfather of grunge who has rocked millions around the world, cuts a contemplative figure as he sits in a small room tucked away in Toronto’s swanky Fairmont Royal York.

But the Soundgarden frontman doesn’t need much prompting to get all animated about The Keeper, his heartfelt lead track for last weekend’s world premiere  Machine Gun Preacher, which stars Gerald Butler as Sam Childers, the former bad boy turned savior of Sudanese war children.

When Cornell wrote You Know My Name for Casino Royale he’d already seen rough footage before he started composing. This gig was different. “The script was enough,” said Cornell, decked out in black knitted jacket, white T and ripped jeans. “I’d heard about the story and it was kind of interesting. Marc [Forster, director] sent me the script and I was off to the races.

“He suggested I look at Sam’s website and it was the images I saw that inspired the lyrics and music… Sam has a directness I hadn’t seen before. These kids suffered in ways I’ve can’t comprehend… Not a day goes by that I don’t think about what I saw.”

Cornell hooked up with his Pearl Jam buddies at the festival and appears briefly in Cameron Crowe’s documentary about the fellow Seattle rockers, Pearl Jam Twenty. “I loved it. Cameron’s expertise as a filmmaker and his personality totally come across.”

Now he’s getting back to writing songs for Soundgarden’s eagerly awaited first album in well over a decade. “It’s been really good,” he said. “We had a 13-year break. Oddly enough it just feels like we had a little break. It’s been nothing but fun and positive and exciting, especially writing the music together because it’s a band where everybody contributes. It brings something out of me as a songwriter that only comes form those relationships. You can’t fake that chemistry.” The album should be ready for spring 2012.