Distortion is not the test. Volume is not the test either, and a record can be loud enough to blow the windows out of a van without coming within a mile of the genre. The heavy metal music characteristics that settle the question are not one trait a band can buy in a shop but a set of five or six, and the set only works when every part of it is present at once.
The Birmingham four who dropped every string three semitones and rebuilt their riffs on the slack were Black Sabbath, and Master of Reality, released by Vertigo in 1971, is the earliest album carrying the whole set together: a riff that is the song rather than its accompaniment, a rhythm section bolted to that riff, a voice pitched over the top of both and a tempo that marches where the blues had rolled.
A sheet of handmade paper holds together because of one movement. The vatman lifts the mould clear of the pulp and shakes it twice while the water drains, once along the frame and once across it, so the fibres settle in two directions and grip each other, and a sheet made without that second shake comes off the felt in strips. Heavy metal is assembled the same way. Every one of its characteristics turns up on its own somewhere else in rock music, and what makes a record metal is that they cross.
The heavy metal music characteristics begin at the guitar
The first characteristic is architecture rather than sound. Through most of rock the guitar answers the singer and fills the gaps around a chord sequence, while in heavy metal the riff is written first, the verse is laid over it and the vocal line arrives last, fitted to a figure that was finished before anybody sang a word. Beyond dispute, the riff came first. It is also not developed the way a theme is developed: it is repeated, and the repetition is the argument.
Gain supplies the weight. A charcoal burner heaps turf and earth over a stack of cordwood and keeps it starved of air for days, so the wood cooks black without once breaking into flame, and an overdriven amplifier treats a signal in that same spirit: the peaks of the wave come back with their tops cut flat, the circuit throws off harmonics nobody played, and a bare root and fifth thicken into a sound with real tonnage behind it. Roll the gain back and the riff goes thin enough to lose under a hi-hat.
Two habits of the hands finish the picture. The palm of the picking hand rests against the strings at the bridge and cuts every note short, which is where the chug under a verse comes from, and the second guitarist takes the same line a third higher, which gives a figure played on wood and wire the carrying power of a brass section.
The West Midlands five who put a short instrumental overture in front of the riff on a 1982 album answered to the name Judas Priest, and when "The Hellion" hands over to "Electric Eye" on Screaming for Vengeance, Glenn Tipton and K.K. Downing run the same line a third apart and leave no room anywhere in the middle of the record for a keyboard, a horn or a second thought.
The riff is not developed. It is repeated, and the repetition is the argument.
The engine room, and the tempo it keeps
The drums do a job a listener notices only once it stops. The kick lands on the beat and the snare on the backbeat, both close to the grid, and the kit is not there to comment on the riff but to nail it to the floor of the bar. Double kick drumming belongs to the style without being demanded by it, and most of the records that built the thing manage without.
The bass has the least freedom of any instrument in the room. A blues or hard rock player walks between the chords, while the heavy metal bass tracks the guitar figure note for note an octave down, which is why "Children of the Grave" arrives as a single object with Bill Ward's toms shoving it from underneath rather than as three musicians in conversation. A bass that wanders here does not add colour. It blurs the edge the whole style stands on.
The band out of South Yorkshire that carried four singles into the British chart in 1980 was Saxon, and Power and the Glory, released by Carrere in March 1983, is the record that put the band at the head of the hall rather than just on the bill. Heavy metal can sprint and it can crawl. Its plainest work is done at the speed of people marching with weight on their backs.
The voice, and why it never confides
The singer is the characteristic argued about hardest and the one that bends furthest. What does not bend is the posture. The voice is aimed at the back of the hall rather than into the microphone, sits above the chord instead of inside it, and carries the melody the guitars are too busy to hold, and inside that brief a tenor at full stretch, a baritone, a shout and a voice with the smoke left in it all pass without comment.
Every practitioner of the style observes one prohibition anyway: nobody leans in and tells a secret. The subjects follow from the posture, and the list is short and old, war, myth, damnation, machinery and the audience itself, which counts as a characteristic only in the weak sense. Those subjects travel with the music without ever defining it. A record about none of them is still heavy metal, and a record about all of them can easily be something else.
What is not a heavy metal characteristic
Four traits get mistaken for the thing itself, and every one of them is shared with music nobody files here. Distortion is the first. The three from Aberdeen, Washington, whose guitars were as filthy as anything in the genre called themselves Nirvana, and no amount of gain turns Nevermind into a metal record, because those songs are chord sequences under a vocal line and the riff travels as a passenger.
Volume is the second, and the Australians who have played louder than most of the bands named here, and who have never once straightened the shuffle out of the rhythm, are AC/DC. Speed is the third, since a fast record with a swing underneath it is a fast rock and roll record and nothing more. The fourth is the imagery, the black sleeve and the occult title, which any band with a printer can have by Friday.
The proof runs in the other direction as well. Turbo, released by Columbia on 7 April 1986, put Roland GR-700 guitar synthesisers through the same amplifiers and drew a complaint from the audience that has followed the band ever since, and the album is heavy metal all the same, because the riff still writes the song, the bass still shadows it and the voice still goes over the top of both. Swap one trait and the set holds. Pull the riff out and the whole thing falls in.
Where the test bends
The border cases bend the test in a pattern rather than breaking it. Doom keeps every characteristic and drags the tempo down until a single chord takes most of a bar to land, thrash keeps the riff and trades the singing for a bark, and the extreme genres kept the guitars and threw the clean voice out of the window. All of them are measured against the same short set, which is why the arguments about them are so fierce and so quickly over.
Where the set came from, and which bands brought which part of it between 1968 and 1976, is the longer account. The heavy metal music characteristics answer one question only, which is what the music is.
They do not touch why people love heavy metal, a question with a longer and considerably stranger answer, and one that no checklist of traits has ever reached.
