Mac Davis, a country music legend as a singer and songwriter, has passed away at the age of 78, following heart surgery in Nashville.The singer's family released a brief statement on Tuesday, revealing he fell'critically ill' after the operation, though now his manager Jim Morey confirmed his death in a statement on his Facebookpage.'It's with a heavy heart that I announce the passing of Mac Davis. He was surrounded by the love of his life and wife of 38 years, Lise, and his sons Scott, Noah and Cody,' Morey began.