Play somebody a thrash record and a heavy metal record back to back and they will tell you the first one is faster. That is true and it is the least interesting thing about it. Speed is the symptom. What actually separates thrash from everything around it is a set of specific physical decisions, taken in the hands and the wrists and the throat, and once you can hear them individually you can identify the genre from a single bar with the tempo removed.
There are six of them. None requires any musical training to hear, and all six have to be present before the word applies.
One: the right hand never alternates
Almost every fast guitarist in the world picks alternately, down and up and down again, because it is twice as efficient. Thrash refuses. The rhythm guitar is downpicked, every note struck on the downstroke, at tempos where that is genuinely difficult and where the easier option would sound wrong.
The reason is what the downstroke does to the front of a note. Every stroke arrives with the same attack and the same fractional silence in front of it, so a run of eighth notes lands as a row of separate blows instead of a continuous smear. An alternate picked run of the same notes at the same tempo sounds smoother, rounder and weaker, and it is the single fastest way to hear that a band has not done the work. James Hetfield holds it through the whole of Battery. That is not a stylistic preference, it is four minutes of manual labour performed to a tolerance.
Two: the heel of the hand is on the strings
Palm muting is the other half of the same gesture. The fleshy edge of the picking hand rests on the strings just ahead of the bridge, damping them enough to kill the ring while leaving the pitch intact, and the result is the chug: percussive, pitched, and dry enough for a drummer to lock onto.
Lift the hand and the same riff turns into open chords and the whole thing collapses into ordinary heavy metal. The distance between those two sounds is about three millimetres of hand position, and it is the difference between two genres.
Three: the riff walks by half steps
What the left hand plays is largely chromatic. A thrash riff sits on a low open string and walks upward a semitone at a time, or hammers a pedal note while a second voice climbs above it in half steps. There is very little blues in it and almost no pentatonic swagger, which is precisely what the heavy metal it grew out of was made of.
This has a structural consequence that matters more than the sound of it. Because the riff is a line rather than a chord progression, the song cannot be about its chorus, and thrash bands wrote five and six distinct riffs per song and arranged them like paragraphs. Listen for the moment a riff hands over to a completely different one with no transition to smooth the join. Heavy metal returns to things. Thrash moves on from them.
The distance between the chug and ordinary heavy metal is about three millimetres of hand position.
Four: the snare is on the upbeat, several times a second
The drums are where the punk parentage is audible and where it is least disguised. The skank beat came straight out of hardcore: kick on the downbeat, snare on the upbeat, hi-hat keeping eighths, driven until the snare is landing four or five times a second. It is trivially simple to write and genuinely exhausting to play, which is why a thrash record sounds like effort even at conversational volume.
The double kick then dates the record almost to the year. The first generation used it as punctuation, a burst of six or eight notes to shove a section forward or fill a bar under a riff change, and then got off it. When you hear the double kick running continuously underneath everything, you have either left thrash or arrived very late in it.
Five: the voice is pitched, and you can understand it
Thrash vocals are barked. Not sung, not growled: pitched speech delivered at the top of the chest, hard consonants pushed forward, phrased rhythmically so that the voice doubles the riff rather than floating over it. It is a percussion part with words in it.
This is the most reliable single test in the genre and it is worth stating flatly. A death metal growl is produced with the false vocal folds, is deliberately unpitched, and treats the words as texture. A thrash bark is pitched and intelligible, and the words are the point of it. If you cannot make out what the singer is saying, whatever you are listening to is not thrash, no matter what the guitars are doing.
Six: the production hides nothing
The last marker is not played by anybody. Thrash records are mixed dry, close and separated: guitars pushed to their own sides, the snare forward with almost no reverb on it, the low end held under control rather than left to swell. Put reverb on this music and it turns to porridge, because the tail of one chord smears into the attack of the next and the palm mutes lose their edge.
Which is the whole point of the exercise, because a listener is meant to be able to take the riff apart while it is still playing. The German bands chose the opposite deliberately and got a wall rather than a diagram; that is a different answer to a different question, and it is why a Kreator record and an Exodus record made in the same year do not sound as though they come from the same planet.
| Marker | Present | Absent |
|---|---|---|
| Downpicked rhythm | Notes land as separate blows | Smoother, rounder: speed metal or hard rock |
| Palm muting | The chug, pitched and percussive | Open chords: heavy metal |
| Chromatic riff writing | Half step walks over a pedal note | Blues and pentatonic: heavy metal |
| Skank beat | Snare on the upbeat, several a second | A rock backbeat: heavy metal |
| Barked, intelligible vocal | Words audible, pitched delivery | Growled: death metal. Sung: speed or power metal |
| Dry, separated mix | Every part audible under speed | Room and wash: black metal, or the German dialect |
What this rules in, and what it rules out
Apply the six and most of the perennial arguments settle themselves. A band with a clean melodic singer over downpicked chromatic riffs is speed metal. A band with all six markers except the vocal, which is a growl, is death metal, and Possessed sit exactly on that line, which is why they get claimed by both sides. A band that has kept the palm muting and the half time riff but thrown the speed away is playing groove metal, which is what several thrash bands became after 1990.
And a band that has the speed and nothing else is simply a fast band. That is the commonest failure among imitators: the tempo is easy to copy and the right hand is not, so the records sound quick and weightless at the same time. Every one of these six decisions costs something to execute, which is precisely why they add up to a genre rather than a style, and it is the mechanical half of the chapter this belongs to. The border that causes more argument than all the others put together is Thrash Metal vs Death Metal.
