THE TOLLING bell, the sound of fierce, driving rain, harsh wind; the opening track of Sabbath's debut is the sound of pure darkness that remains unparalleled to this day. And that's before Tony Iommi unleashes the heaviest guitar riff ever.

Once again, the grim future of a nuclear world raises its head, as Ozzy warns that 'You children of today are children of the grave' over a devastatingly heavy riff.

A chilling vision of the seemingly inevitable Cold War nuclear winter, the wah-wah riffs that powered this slow march into the grave matched the bleakness of the lyrics. 'Reflex in the sky warn you you're gonna die/Storm coming, you'd better hide from the atomic tide'.

Sabbath's later years weren't exactly a goldmine of awesomeness, but the odd ripping track such as this still turned up from time to time. Four minutes of anthemic metal brilliance.

Adding a touch of prog to their usual power trio riff bombardment was a bold move, but one that paid off. One of Dio's finest vocal performances with Sabbath.

IN THE '70s Tony Iommi couldn't take a shit without coming up with riffs as hummable as they were colossal. Exhibit #937, the mammoth wall of fuzz that leads 'Into The Void''s elephantine charge.

The air-guitar hero's weapon of choice. If you haven't mimed along to 'Iron Man's fuzzed-up riffs at least once, then you've clearly never heard it. Remedy that immediately.

OZZY OUT, Ronnie James Dio in, and a change of direction away from their early monolithic riff-fests towards a slicker, bigger sound. Could the ex-Rainbow shrieker fill the Double-O's shoes? Look, it's Dio, abso-bloody-exactly he could.

Along with Tony Iommi's monolithic riffs, Geezer Butler's rolling bass grooves were a pivotal part of the classic Sabs sound, displayed here in gloriously heavy style. Proof that bass solos, occasionally, are acceptable.

WRITTEN IN the studio in half an hour as a filler track, leathery-faced DJ Tony Blackburn dubbed it the worst thing he'd ever heard when it sailed to the top of the charts. Which, on reflection, wasn't such a bad selling point.

A return to massive heaviness after 'Vol 4', this encapsulates everything you want from a Sabbath song; slow, heavy riffs, thunderous drumwork and Ozzy's tortured wail. Sabbath Bloody Sabbath indeed.

Tony Iommi just can't help writing massively weighty riffs. But as 'Sleeping Village''s dreamy, acoustic parts show, there's more than one way to be heavy.

When you get cocaine delivered in industrial soap-powder boxes, you may be overdoing it a teensy bit. On the upside, it makes for a cracking song about the ups, and downs, of Satan's dandruff.

The massive groove that pumps through 'Supernaut' makes it one of Sabbath's most danceable tunes. Which would be great, if it didn't these days act as the signal for middle-aged men to drop all dignity and begin bopping shamelessly.

The blueprint for '90s grunge, the riffs that fuelled this ode to Mary Jane were as juicy as the weed that inspired lines like 'You introduced me to my mind'.

CONSTANTLY ON the lookout for new ways to be heavy, Tony Iommi sped up his usually toe-tapping pace on 'SOTY', giving the future NWOBHM something to plunder relentlessly. Good job.

A harmonica-fuelled display of their blues roots, perfectly demonstrating what Sabbath were doing with their influences. Interestingly, indie types the Kaiser Chiefs use this as their intro music.

In the 1970s, as now, war is bad news. Killer as it is, 'War Pigs'' scathing attack on the men behind the battles is sadly as poignant now as it's ever been.

Opening their fourth record, the imaginatively titled 'Volume 4', their trademark overbearing malevolence took a back seat here. Still rocks like a bastard, mind.