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Joe Perry's solo album, memoir, and Aerosmith tour aren't the only things occupying the rocker's time.  He's also working on "a private thing" with Paul McCartney

The guitarist tells The Chicago Sun-Times the former Beatle is "the great ego leveler."  Perry explains that at the session, which also featured Alice Cooper and Johnny Depp, the three of them were "all looking at each other like open-mouthed kids," thinking "hey, we're sitting here with Paul McCartney!"  He adds that the rock legend is really nice, and is great at putting his collaborators at ease. 

Perry says they recorded their song together in the studio, and just kept playing it until they had a take they liked.  

But Joe won't offer any details on the project, explaining that they're keeping it "under wraps for now."  But he says when the time is right, they'll make an announcement. 

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