Tim McGraw’s 10th annual Swampstock celebrity concert and softball challenge is set for Sept. 19 at the Tim McGraw Sports Complex in Rayville, La. Already confirmed to appear with McGraw and wife Faith Hill are Martina McBride, Jeff Bates and McGraw’s current tourmates, Big & Rich and the Warren Brothers. Tickets go on sale Saturday (Aug. 28) on McGraw’s official Web site and at all Ticketmaster outlets. Money raised at Swampstock will be used to assist charities in Northwest Louisiana. Previous events have benefited a variety of causes, including Rayville’s Dixie League Baseball and the Steve Colvin Memorial Scholarship Fund.