I don’t remember the first time I heard “Tangled Up In Blue.” Bob Dylan was one of those artists I grew up with, like Woody Guthrie and Paul Simon, and it was my mother’s favorite song of his. “Tangled Up In Blue” begins “Blood on the Tracks,” Dylan’s greatest album, which turns 40 this week. As a work of musical genius, the song shines especially bright today, having gone untarnished by the decades. It is a work of singular wonder and beauty, and although Dylan wrote great songs before and after “Tangled Up in Blue,” it remains perhaps the closest to perfection he has ever come.

Although the instrumentals themselves are nothing technically notable, they do their job: the guitar’s small circular pattern pulls in the listener, and once the drums and bass kick in a second later, there’s no chance of escape. There’s a certain calm to this song, partly a result of the laid-back groove and partly from Dylan’s voice, which sounds smooth and refined in a way that it never had before, echoing with a sort of omniscience. He sings with the weariness of a man who knows he has seen all there is to see; he carries supreme confidence in his own awareness. This might be Dylan’s finest vocal: He abandons both the rough-hewn folk-singer persona of his early career and the electric rockstar he played in the mid-’60s, when his voice, full of scorn and spite, crashed and broke in cresting waves upon the protests of viciously hostile crowds. No — this is Dylan in total, quiet command, and his voice rings with an indelible permanence through the song and the entire album.

Despite the song’s sublime sound, its greatest strengths lie in its lyrics. Dylan is the modern Bard, and this is his masterpiece. His lyrics ramble from a tumultuous Brooklyn Heights to a seedy Midwestern strip club, from the Great North Woods all the way down the Mississippi to Delacroix, from the past to the present and back again, switching at whim between the first person and the third. Each verse is a vignette of incredible power and vividness, and the unforgettable details jump out like embers shining in the dark. “I just kept looking at the side of her face/In the spotlight so clear,” he sings, carrying the pain of loss and the joy of rediscovery in two short lines. Or maybe the grim resignation of departure weighs heaviest: “We drove that car as far as we could/Abandoned it out West/Split up on the docks that night/Both agreeing it was best.” These lyrics create images far greater than the words themselves. They evoke an entire era — the glorious, glamorous 1960s, full of revolution and madness and aspirations to utopia, quickly fading from view in the cultural chaos of the mid-1970s. It is a hesitant lament to a time most of us never knew, whose legacy remains uncomfortably uncertain.

But in some sense, it’s wrong to talk about “Tangled Up In Blue” as a single song. Dylan has officially released at least four versions of the track, and bootlegs of other live performances abound. And each time he performs it, something different emerges — maybe he’s tweaked the lyrics a bit, or changed the melody around, or decided to add one instrument and remove another. The album version of “Tangled Up In Blue” has a certain hope to it: Even though his relationships have fallen apart over the years at the mercy of cultural shifts, there’s still some unreached promised land out there. On his European tour in 1984, he changed around most of the lyrics, and while the essential message remained unchanged, the images are richer and darker. He and his lover still encounter each other at a strip club, but this time the experience is uncomfortably visceral: “I could feel the heat and the pulse of her/As she bent down to tie the laces of my shoe,” he sings. In this version, sailors come close to drowning, and widows go penniless.  Dylan claims he likes this version best, and maybe that’s because the visions are eerier. They’re starkly uncompromising; they carry more of the ages with them.

But Dylan’s greatest reinterpretation of his own song came before he decided to alter the lyrics. On June 7, 1978, at the Los Angeles Coliseum, he played a version of “Tangled Up In Blue” so profoundly haunting as to be an entirely different work altogether. Gone is the powerful strumming; absent is the gleaming twinkle of hope. Instead, a soft guitar slowly marks the beat behind a mournful, beautiful interplay between the organ and tenor saxophone. No light seeps into this version of the song, no chance of reunion or redemption. The lyrics, now, are in the third-person, as Dylan distances himself from the events, a conscious attempt to put it all behind him. Perhaps, in the middle of the national tumult of the Carter presidency, Dylan just couldn’t bear the heavy burden of the memories of previous years. Perhaps he needed to move on, reinvent his music and persona, change his clothes, his hair, his face. Whatever happened, happened, this version says — it is irretrievably past.

But time must go on, as it does, and the present never ends. For me, one of the later lyrics in the original version hits hardest: “The only thing I knew how to do/Was keep on keeping on/Like a bird that flew/Tangled up in blue.” Is there any better expression of solidity and endurance? Dylan’s world has collapsed around him, the friends he once loved have moved on, he can no longer recognize this placed called America. Never mind, though — he’ll keep on keeping on.

And that’s all you can do when you hear this song. At first listen, “Tangled Up In Blue” might not sound so remarkable, but as you listen to it more and more, as the lyrics light their slow-burning fuse in your heart, as Dylan’s voice etches his words into your soul, and as the characters appear increasingly alive, this song becomes real like few others are. Its inescapable story lives on in the mind or somewhere deeper, as integral to human experience as anything Shakespeare or Yeats ever wrote, and the many reinterpretations only expand its reach. Eventually we all get tangled up in blue.