Routinely ranked among the greatest heavy metal albums of all time, The Number of the Beast is the birth of Iron Maiden as we know it, a relentless metal machine lifted to soaring new heights by the arrival of erstwhile Samson frontman Bruce Dickinson.

Dickinson's operatic performance here made him an instant metal icon, challenging even Rob Halford for bragging rights, and helped launch the band into the stratosphere.

The Number of the Beast topped the charts in the U.K., but even more crucially -- with Judas Priest having moved into more commercial territory -- it also made Iron Maiden the band of choice for purists who wanted their metal uncompromised.

Maiden took the basic blueprint Priest had created in the late '70s -- aggressive tempos, twin-guitar interplay, wide-ranging power vocals -- and cranked everything up faster and louder.

The album's intensity never lets up, the musical technique is peerless for its time, and there isn't a truly unmemorable song in the bunch.

Blessed with a singer who could drive home a melody in grandiose fashion, Steve Harris' writing gets more ambitious, largely abandoning the street violence of old in favor of fittingly epic themes drawn from history, science fiction, and horror.

The exceptions are "22 Acacia Avenue," a sequel to "Charlotte the Harlot" that sounds written for Di'Anno's range, and the street-crime tale "Gangland," which Harris didn't write; though the punk influences largely left with Di'Anno, these two definitely recall the Maiden of old.

As for the new, two of the band's (and, for that matter, heavy metal's) all-time signature songs are here.

The anthemic "Run to the Hills" dramatized the conquest of the Native Americans and became the band's first Top Ten U.K.

single.

It features Maiden's trademark galloping rhythm, which in this case serves to underscore the images of warriors on horseback.

Meanwhile, the title track's odd-meter time signature keeps the listener just slightly off balance and unsettled, leading into the most blood-curdling Dickinson scream on record; the lyrics, based on nothing more than Harris' nightmare after watching a horror movie, naturally provoked hysterical accusations of Satan worship (which, in turn, naturally provoked sales).

"Hallowed Be Thy Name" is perhaps the most celebrated of the band's extended epics; it's the tale of a prisoner about to be hanged, featuring some of Harris' most philosophical lyrics.

It opens with a superbly doomy atmosphere before giving way to a succession of memorable instrumental lines and an impassioned performance by Dickinson; despite all the tempo changes, the transitions never feel jarring.

Elsewhere, "The Prisoner" is a catchy retelling of the hit British TV series, and "Children of the Damned" is a slower, heavier number patterned after the downtempo moments of Dio-era Black Sabbath.

CD remasters integrate "Total Eclipse," first released as the B-side of "Run to the Hills," into the running order.

Though some moments on The Number of the Beast are clearly stronger than others, the album as a whole represented a high-water mark for heavy metal, striking a balance between accessible melodicism and challenging technique and intensity.

Everything fell into place for Iron Maiden here at exactly the right time, and the result certainly ranks among the top five most essential heavy metal albums ever recorded.

A cornerstone of the genre.