Most Iron Maiden fans rave about thealbum, while others think it's overrated. But everyone agrees it's the record that gave birth to Iron Maiden's unique sound.

Released on Feb. 2, 1981, Killers featured a much bigger, better sound than Maiden's self-titled debut album. And that is thanks to Maiden uber producer Martin Birch, whom the band first believed was too big to work with them.

Prior to recording their 1980 debut, Maiden bassist and leader Steve Harris originally wanted Birch to produce the record, but didn't think someone of Birch's stature would want to work with the band at the time, when hardly anyone knew who they were. "We all talked about him, but we thought, like, 'We’re not worthy'," recalled Harris.

Birch had just been busy in 1979 working on Black Sabbath's massive Heaven and Hell album, and he'd also worked with Deep Purple, Rainbow and Wishbone Ash, so it's no wonder Harris thought he was out of their league.

But Birch was certainly up for the task. He met Harris, likely in June 1980, and told him he would have loved to have worked on Maiden's debut album, which ended up being sloppily produced by Will Malone. From there, the rest is history and Birch would hone Iron Maiden into one of the greatest metal bands of all-time, working on every album through 1992's Fear of the Dark.

Killers Essentially Recorded Live in Studio

The first thing Birch - who was dubbed Martin 'Headmaster' Birch on the Killer's liner notes (one of many nicknames the band bestowed upon him) - did was set up mics in one room and get the band to play live. He told the band to play the songs as if they were playing a concert, and they'd work on overdubs and different takes from there. They recordedin just three months (November 1980 - January 1981) at Battery Studios in London.

Guitarist Adrian Smith, who had just joined the band after they'd booted Dennis Stratton, recalls how Birch was quite the taskmaster in the studio - fair but firm: "I’d never worked with a producer who was so totally involved in the whole process. He was a good laugh, but when we were working, he cracked the whip," said Smith.

What Birch did on Killers was help create the unique sound fans instantly recognize as Iron Maiden. There's a dark tone edged into the overall sound, with a low end, fat drum sound, guitars that are perfectly slotted in the mix, dominant, but not over-the-top bass and Paul Di'Anno's vocals coming through at just the right level. A key to the Maiden sound was how every element of every instrument sound stood out. There was nothing buried in the mix.

Most of the songs were around from when the band had gone into the studio to do their first record, and every track, save for "Killers" (co-written with vocalist Paul Di'Anno) was penned by Harris. And the only two songs that were new were "Murders in the Rue Morgue" and "Prodigal Son", a ballad.

Part of the unique Maiden sound comes on "Murders in the Rue Morgue", where Harris helps create the dark mood in the intro by playing bass harmonics.

There are two instrumentals on the album, the opener "The Ides of March" and the phenomenal "Genghis Khan", which features an amazing beat from drummer Clive Burr and some seriously heavy, thrashing guitar riffs.

"Wrathchild" had originally been recorded on the Metal for Mutha's compilation, released a year before Killers. The version that appears on Killers shows how much Maiden had matured in just a year. Burr's drumming in particular is much more smooth, while the overall sound difference is night and day.

While most rock critics at the time gave Killers unfavourable reviews, it has some of their best songs: "Drifter" and "Purgatory" among them. And Harris still looks back on the album with great reverence, saying "I loved The Number Of The Beast, but I didn’t think it was our best album at the time, and I still don’t."

Killers Artwork Cements Eddie in Maiden Lore

Along with the music, Killers really brought the artwork (see above) of Derek Riggs and Maiden's mascot, Eddie, to the forefront with that instantly recognizable album cover.

It depicts a late night scene in East London near a sex shop where Eddie is gleefully clutching a hatchet dripping blood, while his victim clutches hopelessly in vain to his T-shirt while assorted peeping toms peer down at the scene from behind drawn curtains. It’s become one of heavy metal’s most iconic cover images.

The cover also helps get the listener into the mindset of the album's dark tone and lyrics.

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