Sir Paul McCartney wrote a special letter to Carrie Underwood to give the country star permission to cover the Fab Four?s hit ?Yesterday? as part of an Emmy tribute to the historic events of 1963, which included the Beatles? TV debut in America. Underwood posted on Twitter: ?The coolest thing about singing Yesterday on the Emmys is the sweet letter I got from Paul McCartney giving me his blessing to sing it!?