The members of Lady Antebellum—Charles Kelley, Dave Haywood and Hillary Scott—have spent most of their summer on the road with Tim McGraw on his Southern Voice Tour.

Charles says that the group was recently initiated to the tour by one of Tim's special customs. “It’s really cool. He had the tradition of giving [one of his own] shirts to his opening act,” said Charles during a press conference at CMA Music Festival. “I thought he was just kidding at first. The wardrobe person [on Tim's tour] says it’s something he does. Then one day he brought out a shirt to Dave and me and that was really cool. I wonder how that started. I wonder if there was a new artist [on tour with Tim once] and if Tim was like ‘You’ve got bad style! Here’s one of my shirts. Get started on the right path,’” Charles said with a laugh.

The group will be out with Tim through Aug. 7, which is when they perform at Molson Ampitheatre in Toronto.