Hunter Hayes stepped in for pop star Demi Lovato at a free Independence Day concert in Philadelphia on Thursday (July 4). Lovato was unable to appear due to strep throat. The all-star lineup at the third annual Philly Fourth of July Jam also featured J. Cole, Kevin Hart, John Mayer, Grace Potter, the Roots, Jill Scott and Ben Taylor. Hayes will headline the sold-out Freedom Fest on Friday night in Farmingville, N.Y., with fellow country artists Dustin Lynch, the Henningsens, Lauren Alaina and Lonestar also on the bill.