(hennemusic) Kid Rock  threw one helluva big party on Saturday at Detroit's Ford Field, kicking off his "Born Free" tour while celebrating his 40th birthday with 60,000 of his closest friends (Rock turns 40 on Monday).The Detroit Free Press reports the event was "part stadium spectacle, part nostalgic retrospective, the marathon show explored the breadth of Rock's two-decade catalog, neatly tucking his vintage risqué rap alongside the meatier rock fare of his new "Born Free."

In a night that featured plenty of star power – video messages from Conan O'Brien, Jon Stewart and Jay Leno – there were live musical collaborations with Peter Wolf ("Detroit Breakdown"), Martina McBride ("Care") and the Rev. Run ("Walk This Way") – but it was Sheryl Crow who stood out. She joined Rock for a rare live duet on their hit "Picture" and stuck around for a frisky performance of Free's "All Right Now," including a bout of close dancing that got the crowd shrieking.