Some bands have a horn section; the Grateful Dead had their own poet. Mr. Hunter — who died on Sept. 23 at the age of 78 — never sang on record or played an instrument with the band. But he wrote the words for their most iconic songs: “Truckin’,” “Uncle John’s Band,” “Friend of the Devil” and more.

Mr. Hunter refused to explain what his words meant, preferring to let the songs speak for themselves. In making the 2017 documentary “Long Strange Trip,” Amir Bar-Lev managed to get the reclusive Mr. Hunter on film. In that interview, Mr. Hunter recited the inscrutable lyrics to “Dark Star,” (“Glass hand dissolving in ice petal flowers revolving,”) and then simply stated, “It says what it means,” as if this were self-evident. And who knows? Perhaps it was.

It takes a particular form of genius to sustain an artistic collaboration, a relationship that may have more in common with a marriage than a business. John Lennon and Paul McCartney brought out the best in each other — for a while, anyway. So did Gilbert and Sullivan, and Simon and Garfunkel, and the Everly Brothers. It’s not always clear where Gillian Welch’s songs end and David Rawlings’s begin; Mr. Rawlings has described himself as “being one half of a group called ‘Gillian Welch.’”

Robert Hunter would have bristled if anyone had the gall to suggest he was half of a group called “Jerry Garcia.” But he did possess an uncanny ability to find the words that expressed the heart of his friend. They’d met as teenagers in Palo Alto, Calif., in 1961, at a local production of the musical “Damn Yankees,” and it is lovely to think of those two young men sitting side by side, listening to the song “Heart”: “You’ve gotta have heart/ All you really need is heart/ When the odds are saying you’ll never win /That’s when the grin should start.”

In their long years as partners, the two would do a lot of grinning. They would weep sometimes, too.