It's the voice that seems to emerge from a steep climb over broken glass and gravel - along with the ever-present gleam in the eye, at once playful and world-weary, and the gruff but self-deprecating demeanor.
On record and on stage, Kris Kristofferson carved out a persona as the outlaw scholar, a poet among cowboys alongside his Highwaymen partners, Willie Nelson, Johnny Cash, and Waylon Jennings. On screen, he long ago became Hollywood's go-to actor for grizzled wisdom.
At 80, Kristofferson has evolved his image again - purposely or not. While he performed alone at the Keswick Theatre on Wednesday, his voice cracked, at times to the point where it threatened to shatter and dissipate completely. Certain turns of phrase caught in his throat, whether from the emotion of the story or from the wear on his vocal cords, it could be hard to tell. A line might get interrupted by a sudden gust of throat-clearing, a song disrupted by forgetting to swap in the right harmonica for the tune.
In short, Kristofferson showed the frailties and vulnerabilities of age on that stark stage, dressed head to toe in black and roughly picking at his acoustic guitar. Some of that is the inevitable ravages of time, as he addressed in the title track from his most recent album of new material, "Feeling Mortal." Some of it creeps in with the knowledge of his health struggles in recent years, as he suffered from memory loss caused by Lyme disease that was misdiagnosed as Alzheimer's.
And some of it was most likely his actor's instinct for wringing the emotion out of a lyric, summoning a tear for the wistful "Jody and the Kid" or chuckling at his own turns of phrase in "The Silver Tongued Devil and I."
As always, Kristofferson resembled one of the characters from his songs: wise enough to recognize his shortcomings, foolish enough to repeat them again and again. Slyly duplicitous, a bit self-destructive, but ultimately well-meaning - or, as he put it in one of those lines that made him laugh knowingly at himself, "just like a human."
Kristofferson kept up his taciturn guise throughout the 90-minute set, stringing together more than 30 songs with little more than a quickly barked "thank you" between them. A quick swipe of his handkerchief did elicit a wry apology that the audience had to "pay a lot of money for a ticket to watch an old fart blow his nose," but that was the extent of the repartee.