For years, Bob Dylan fans have spoken in a sort of hushed awe about the longest song he ever released, “Highlands,” an album side-length 1997 track that ran 16 minutes and 31 seconds. Now, 23 years later, he’s slightly outdone himself. As the clock struck midnight on the east coast Friday morning, Dylan released a new song, “Murder Most Foul,” that has a running time just seconds shy of the 17-minute mark — and it’s an epic free association on the 1963 assassination of President John F. Kennedy.

Little information was given about the surprise track, except for a brief statement from Dylan himself:

“Greetings to my fans and followers with gratitude for all your support and loyalty over the years.

“This is an unreleased song we recorded a while back that you might find interesting.

“Stay safe, stay observant and may God be with you.

“Bob Dylan”

A Dylan representative said the statement was all the information they would be releasing about the song, so whether “a while back” means a matter of months or many years remains a mystery.

Dylan’s tender vocal tone — a trademark of his more recent shows and recordings — and elements of the song’s minimal bed of violin, piano and light percussion quickly had hardcore fans guesstimating that the tune might actually be of fairly recent vintage.

His last album of original material, “Tempest,” came out in 2012, although he has released three sets of his interpretations of songs from the Great American Songbook in-between, the last of which was the triple-album “Triplicate” three years ago. Rumors have been rampant that this year Dylan might be releasing his first album of self-penned songs in eight years, but there’s been no confirmation of that.

The lyrics of the monumental track will fascinate Dylanologists who’ve waited years for something fresh to dissect, since there’s literally half an album’s worth of lyrical material just in one track here.

In verses that proceed freely enough that it’s not always easy to break them down into separate stanzas, the lyrics often speak extremely literally of the Kennedy assassination, with a bent toward conspiratorial takes on the event. But as the song goes along it breaks more freely into a pop-culture fantasia.

Dylan frequently references or riffs on 1960s events, catchphrases or titles, with lines that include: “The Beatles are coming, they’e gonna hold your hand” (the arrival of the Fab Four in America in early 1964 is regarded by some as a tonic to the lingering depression from the assassination); “ferry cross the Mersey and go for the throat” (only part of which is a nod to Gerry and the Pacemakers); “Tommy can you hear me, I’m the Acid Queen,” and “I’m going to Woodstock, it’s the Aquarian age / Then I’ll go to Altamont and stand near the stage.”

Dylan doesn’t have his head entirely in the ’60s: “Frankly Miss Scarlett, I don’t give a damn” also comes up for a citation. And eventually, so do — moving into the ’70s, and beyond and back — Lindsey Buckingham and Stevie Nicks, Don Henley and Glenn Frey, the Allman Brothers Band’s Dickey Betts, “Only the Good Die Young, “Nightmare on Elm Street,” Buster Keaton, Harold Lloyd, Art Pepper, Oscar Peterson, Stan Getz, “Charlie Parker and all that junk,” Nat King Cole, Marilyn Monroe, John Lee Hooker, Wolfman Jack, Patsy Cline, Houdini, “Wake Up Little Suzy,” “Let the Good Times Roll,” “The Old Rugged Cross,” “Down in the Boondocks,” “The Merchant of Venice,” “Memphis in June,” “Moonlight Sonata,” “Play Misty for Me,” “Lonely at the Top” and “Lonely Are the Brave.”

Occasionally, Dylan directly marries his pop-culture references and the assassination, as when he sings, “You got me Dizzy Miss Lizzy, you fill me with lead.” Or: “What’s new pussycat, what’d I say / I said the soul of a nation been torn away.”

When it comes to the actual assassination, Dylan doesn’t skimp on the details: “They blew off his head while he was still in the car,” he sings in the first stanza. Later on, he traces the car’s frantic exit away from Dealey Plaza in Dallas, even taking the first-person point of view of the deceased Kennedy: “Riding in the backseat next to my wife / And it’s straight on into the afterlife / I’m leaning to the left I got my head in her lap…” He gets specific about details following the death, too — like “Johnson sworn in at 2:38.”

He also takes the point of view of Kennedys assailant — or, in his view, assailants — singing provocative lines like, “We’ve already got someone here to take your place,” or, of Kennedy’s brothers, “we’ll get them as well.”

Dylan’s fascination with the Kennedy assassination is nothing new — it dates back to 1963. At least, Robert Shelton’s biography, “Bob Dylan: No Direction Home,” recounts an incident three months after the killing when the singer and his fellow travelers took a detour to Dealey Plaza and “took the station wagon along Kennedy’s path,” “appraised the theory that Oswald acted alone” and “started acting like a detective.”

In the song’s view, the killing of JFK, “right there in front of everyone’s eyes,” is the “greatest magic trick” — and one he presumably thinks has some relevance in 2020.