Dave McClure's video: DON T LET THE OLD MAN IN Great song written by Toby Keith performed by Dave McClure

Pre concert sound and lighting check. Toby Keith knows a good hook when he hears one. And no one weaves a tale quite like Clint Eastwood. That the two were sharing a golf cart last year at Eastwood’s charity tournament in Pebble Beach, Calif. is both a testament to their friendship and a stroke of good fortune. The encounter led Keith to pen the beautifully haunting song that lingers at the end of The Mule. The Eastwood-directed and starring film, in theaters now, is based on the true story of a WWII veteran in his 80s who takes a job as a courier for a Mexican drug cartel. Out on the green, Eastwood shared that he’d be starting work on The Mule in two days, which also happened to be his 88th birthday. Struck by Eastwood’s relentless energy at an age when many are content to sit and reflect, Keith asked how he keeps going. “He said, ‘I just get up every morning and go out. And I don’t let the old man in,’ ” Keith recounts. “And I thought, I’m writing that.” What was to become “Don’t Let the Old Man In” transfixed the country singer/songwriter, who had soaked in enough about the film and Eastwood’s character to take a stab at a song. “People were talking to me and they would say, ‘Did you hear what I just said?’ And I was like, ‘No,’ because I wasn’t listening to any conversations. I was consumed by ‘Don’t Let the Old Man In.’ I worked so hard on it,” Keith says. “When I finally sang the line, I thought, it’s got to be dark, it’s got to be a ballad and it’s got to be simple.” In what turned out to be another stroke of serendipity, Keith was under the weather the day he cut his demo. “I was sick as a dog that day. I was coughing and sneezing and thinking, this is terrible,” he recounts. “I gave it the best vocal I could that day, and I sent it off. It’s a real raspy, sleepy, tired, sick vocal. I said, ‘Well now you’ve got a reference, and I’ll go back and put a vocal on it for you.’ ” To his surprise, Eastwood called immediately. “He said, ‘I’ve got a spot in the movie and I’m putting it in there.’ And then Warner Bros. called asking did I read the script before I wrote this song because it fits perfectly.” To his greater surprise, Eastwood didn’t want to change a thing. “He wanted it sick and tired and dark like that,” Keith says. The song’s aesthetic, at once emotionally resigned and quietly triumphant, turned out to be right in tune with that of the film. Its refrain, “Many moons I’ve lived/my body’s weathered and worn/Ask yourself how old you’d be if you didn’t know the day you were born?” was inspired by another anecdote Keith had been carrying around about the grandmother of his 65-year-old friend who never had a birth certificate and didn’t know her age. “I didn’t try to take what he told me about the movie,” Keith says of his muse. “I tried to take the character he told me about, and look through his eyes and think that maybe if you were 40 and found out the cartel is putting drugs in your pecans you might say, ‘Whoa, I don’t want to do this because I don’t want to spend 40 years in prison.’ “But if you’re 85? What’s a life sentence at 85? I got the chance to make tens of thousands of dollars.” Keith pauses. “I might try it at 85."