Even if you don't know anything about Let It Be's messy history, one listen to the Beatles' penultimately recorded, last-released album reveals that something just isn't right with the once-fab band. The abbreviated nature of some of the songs, the tossed-off casualness of others – this doesn't sound much like the group behind the meticulously assembled Sgt. Pepper's Lonely Hearts Club Band and the separate-but-still-together White Album.

It's been well-documented that George Harrison, John Lennon, Paul McCartney and Ringo Starr weren't getting along like they used to by January 1969, when the first sessions for the Beatles' next album, Get Back, started. The toll of Beatlemania, not to mention the itch to make music outside of the tight circle that consumed their lives over the past decade, was beginning to weigh heavily on everyone. (Various Beatles were quitting regularly by this point.)

That's why 1968's The Beatles was essentially four solo albums for the price of a double record. And that's why, when they reconvened at the start of the final year of the decade in which they came of age, they decided on no studio tricks, no outside influences and no pressure. Things didn't quite work out that way. Get Back was shelved, Abbey Road was recorded and released instead and those early 1969 sessions were later remixed by Phil Spector as Let It Be, with some inside grumbling, then released in May 1970.

The excellent six-disc (five CDs, one Blu-ray) Super Deluxe Let It Be Special Edition doesn't capture the tensions that reportedly spoiled the sessions. But it does come close to bottling the occasional messiness that went into the recordings as the Beatles relocated from Twickenham Film Studios to Apple Studio to a Savile Row rooftop, and attempted new originals, old originals and a bunch of covers in an effort to salvage something. (The Beatles: Get Back book collects dialogue transcripts and photos from the sessions to give you an even more detailed document of the period.)

In addition to a newly mixed Let It Be from Giles Martin and Sam Okell, the box includes the original 1969 Get Back album assembled by engineer Glyn Johns and more than two dozen session and rehearsal leftovers. (Alas, only one track from the famous Apple rooftop performance, the "Get Back" single B-side "Don't Let Me Down," is here.) It's not the extensive dissection the Special Edition could have been – more than 150 hours of material exists – but like previous multidisc collections dedicated to Sgt. Pepper, the White Album and Abbey Road, this upgraded Let It Be uncovers some fresh perspective.

The new mix is revelatory at times, sweeping away some of Spector's mud and elevating previously buried elements you probably never knew were there: "I Me Mine" bounces now, "Let It Be" sounds even more hymnlike, the jagged edges of "I've Got a Feeling" are suitably tempered by Billy Preston's electric piano. But the real revelations can be found in the two discs of outtakes and alternate versions.

Take 10 of "Let It Be" starts with a piano-seated McCartney goofing on the Beatles' first U.K. Top 10 "Please Please Me." An all-too-brief cover of the Everly Brothers' "Wake Up Little Susie" that prefaces an instrumental take on "I Me Mine" shows how easy it was for the group to slip into some of its favorite songs. Harrison demos his newly written "All Things Must Pass" for his bandmates, who join in following a solo verse and chorus. And early attempts at five Abbey Road songs (two of them, "She Came in Through the Bathroom Window" and "Polythene Pam," were incorporated into Side Two's sprawling medley) reflect the anything-goes looseness of the sessions.

The official arrival of Get Back here is also welcomed and achieves the sort of stripped-back design that 2003's similar-minded Let It Be ... Naked couldn't quite grasp. (The untidy delivery of the music also makes more sense in the context of a quasi live album.) And that's always been Let It Be's thorn and grace.

By the time the Beatles abandoned the project less than a month after they started, none of the principals wanted anything to do with it. In a sense, Let It Be became a malleable record for anyone with the patience to wade into the mire. Will this Special Edition be the final word on the subject? Probably not; there's much left in the vaults. Consider these 57 songs the latest steps in its evolution.

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