It’s a difficult task to qualify what makes a great album a great one. Over time, it becomes increasingly hard to separate why those older, iconic albums were important in the past from why they’re still relevant in the present. They’ve become so ingrained in history and their relation to that particular context that it leaves us in a biased place when we try to talk about them. I know what that album “did,” which makes it harder to see what that album “does” on its own, independent of the past, which can either hurt an album or help push it into the annals of history.

This is precisely the reason why an album like Badfinger’s 1971 work “Straight Up” becomes forgotten. It was written off by critics as another Beatles clone. It has simply become dismissed to time, even though it’s an incredibly solid and well-put together album. And it’s the same reason why the Rolling Stones’ 1972 album “Exile on Main Street” is so highly regarded, when it’s actually probably one of their weaker works. “Exile” is a great collection of songs, but it’s helped largely by the fact that it came out in the heart of the Rolling Stones’ golden age of albums. It came out in 1972, when the gritty rock sound was really hitting its stride.

“Exile” is a solid effort, but it doesn’t flow well as an album, which might sound incredibly nit-picky, but is perhaps the best way to judge an album. Personal taste aside, does this work as an “album?” Do all the parts come together and the album simply equal that sum total? Or somehow, from all of those pieces being put in all the right places, does it end up equaling something far greater than the mere sum? It is here in this second category where we find the truly transcendent albums. Here, where we find U2’s 1991 magnum opus, “Achtung Baby.”

The album equals far more than a collection of different songs. Together, they create an emotional odyssey, through the heart of rock music and into its sad and contemplative underbelly, from the opening licks on “Zoo Station,” with their iconic industrial sound, through the interlocking guitars on “Even Better than the Real Thing,” with Bono’s crooning hovering over all, straight into the sorrowful acoustics of “One.”

There is a natural flow to the album. We’re taken from the dream of rock ‘n’ roll, where Bono tells us, “We’re free to fly the crimson sky, the sun won’t melt our wings tonight” on “Even Better than the Real Thing,” into “One,” where uncertainty sets in. The introduction of the acoustic guitars echoes the sadness as Bono cries out, “We’re one, but we’re not the same. Well we hurt each other, then we do it again.”

But the greatness of “Achtung Baby” is not only in its embodiment of being a great “album,” in the truest sense of the word, but also in its shocking creativity. U2 was coming off of “Joshua Tree” in 1987 and then “Rattle and Hum” in 1988. They were heading increasingly down a roots-rock sort of road, complete with harmonica solos and opening keyboards by Bob Dylan (“Hawkmoon 269” off “Rattle and Hum”). Then three years passed and no one knew what U2 was planning, though logic would have dictated something in that same vein of reconfigured folk-rock.

But instead they released “Achtung Baby” — an aggressive, electronic and at times, even industrial album. It celebrated rock-star excesses on a song like “The Fly,” as a way of sarcastically and satirically condemning it. They even embarked on the Zoo TV tour as a giant parody of rock superstardom, with Bono donning sunglasses and all-leather garb and calling himself “The Fly,” all of which may get lost in our musical present, where U2 seems almost identifiable by the effects-laden guitar work by The Edge and larger-than-life personas.

But not in 1991. Then, it was unheard of, and entirely unexpected. It’s almost unfathomable to think of something like that happening today in music — an artist completely changing genres of music and going in the direction contradicting everything they’ve done previously. And most importantly, succeeding at it.

This new 20th anniversary edition of the album is absolutely spectacular. I usually don’t care when an album is remastered. It always just sounds the same as the earlier versions — maybe slightly better quality, if one really strains to listen.

But this “Achtung Baby” re-issue is fairly astounding. It has a newfound power in this remastered version, with the beauty of all the instruments able to shine even more clearly than before. And the Deluxe Edition comes with an entire second disc of B-sides, outtakes and alternate versions of various tracks, which is a fascinating listen. There are some great songs on there, and to hear different versions of time-tested favorites is always an intriguing experience.

“Achtung Baby” has been here for 20 years now, influencing and reaching out to people, myself included. It was there when I entered the vast unknown of freshman year and managed to capture my anxieties and my hopes. It was there to connect to when I started dating my girlfriend. And it was there when we broke up.

That’s the beauty of “Achtung Baby.” There is so much power, both lyrically and musically, in every single song. And to be able to shift and reflect whatever our desires may be at a certain time, to be able to transcend any particular moment, both in one’s personal history as well as the album’s own historical context, is indicative of only the best albums of all. “Achtung Baby” is truly one of the best, and with this new remastered edition, it will continue to be for many years to come.

GRADE: A+

Title: “Achtung Baby”

Artist: U2

Remastered release date: Oct. 31