Today is Joni Mitchell's 75th birthday. To celebrate, a bunch of her famous fans are performing at a two-night concert called Joni 75 at LA's Dorothy Chandler Pavilion. Among the performers: James Taylor, Brandi Carlisle, Chaka Khan, Kris Kristofferson, Rufus Wainwright, Emmylou Harris, Glen Hansard, Norah Jones, Diana Krall, Los Lobos, Graham Nash, and Seal.