Metal

History and character

Heavy metal developed between the late 1960s and the early '70s, mainly in the United Kingdom and the United States, out of blues rock, psychedelic rock and acid rock. Black Sabbath's debut album (1970) is generally considered the first heavy metal record; the industrial, working-class environment of Birmingham is cited as one of the roots of their heavy sound. Tony Iommi, who had lost the tips of two fingers in a factory accident, lowered his tuning to reduce string tension and built his style on simple power chords: on Master of Reality (1971) some songs are tuned a step and a half down. The other fathers are Led Zeppelin and Deep Purple.

In the 1970s and '80s the genre took shape with Judas Priest, Motörhead, the New Wave of British Heavy Metal (Iron Maiden, Saxon, early Def Leppard), Dio, Ozzy Osbourne and Scorpions; in the early '80s thrash (Metallica, Slayer, Megadeth, Anthrax), speed and power metal were born, along with Los Angeles glam metal. From the mid-'80s the extreme forms arrived: death metal (Florida, Bay Area), black metal (first wave with Venom, Bathory and Celtic Frost; second in Norway), doom, grindcore. The 1990s brought groove metal (Pantera), alternative and nu metal, industrial, symphonic, progressive (Dream Theater) and Swedish melodic metal; the 2000s metalcore and deathcore; the 2010s djent and post-metal.

Common traits: heavily distorted guitars, often downtuned, playing riffs in power chords and palm mutes; bass doubling the riff; powerful, fast drums (double kick, blast beats) on a bigger kit than rock's; vocals ranging from high, clean singing to growls and screams; modal harmony (Aeolian, Phrygian), chromaticism and the tritone. It is one of the most technical and structured genres in popular music, with a strong culture of virtuosity and production.

Scales and keys

Aeolian (natural minor)

• Formula: 1 2 b3 4 5 b6 b7 — steps W H W W H W W.
• Example in E: E F# G A B C D.
• Characteristic note: b6 (C), which gives the major VI and the epic-melancholic color.
• Diatonic chords in E: i Em, ii° F#dim, III G, iv Am, v Bm, VI C, VII D.
• Use: epic i–VI–VII progressions (I–bVI–bVII in Wikipedia's modal notation), harmonized guitar melodies, choruses.
• Real example: Iron Maiden — The Trooper (riff and harmonies in E minor); Metallica — Fade to Black.
• Common mistakes: always raising the 7 as in harmonic minor: it ruins the Aeolian color.

Phrygian

• Formula: 1 b2 b3 4 5 b6 b7 — half steps 1-2-2-2-1-2-2.
• Example in E: E F G A B C D.
• Characteristic note: b2 (F): the half step above the tonic, the signature of metal (I–bII–I).
• Chords in E: i Em, bII F, bIII G, iv Am, v° Bdim, bVI C, bvii Dm.
• Use: riffs on an open E string pedal with the F (E–F–E), bII–i cadences, thrash and death riffs.
• Real example: Metallica — Wherever I May Roam (Phrygian with an Eastern color); Slayer — many riffs on E–F.
• Common mistakes: using F# out of habit: you lose the color.

Harmonic minor

• Formula: 1 2 b3 4 5 b6 7 — half steps 2-1-2-2-1-3-1.
• Example in A: A B C D E F G#.
• Characteristic note: the raised 7 (G#) and the augmented second F–G#: a "neoclassical" sound.
• Chords in A: i Am, ii° Bdim, III+ C+, iv Dm, V E, VI F, vii° G#dim.
• Use: neoclassical solos (Yngwie Malmsteen, Randy Rhoads), V–i cadences, diminished arpeggios.
• Real example: Ozzy Osbourne — Mr. Crowley (Randy Rhoads, solos in D harmonic minor).

Phrygian dominant (5th mode of harmonic minor)

• Formula: 1 b2 3 4 5 b6 b7 — half steps 1-3-1-2-1-2-2.
• Example in E: E F G# A B C D.
• Characteristic note: b2 + major 3 (F and G#): a "Middle Eastern" and menacing sound.
• Chords in E: I E, bII F, iii° G#dim, iv Am, v° Bdim, bVI+ C+, bvii Dm.
• Use: exotic riffs and leads (Megadeth, Nile, Metallica), technical death metal.

Locrian

• Formula: 1 b2 b3 4 b5 b6 b7 — half steps 1-2-2-1-2-2-2.
• Example in E: E F G A Bb C D.
• Characteristic note: b5 (Bb): the tonic has no perfect fifth, total instability.
• Chords in E: i° Edim, bII F, biii Gm, iv Am, bV Bb, bVI C, bvii Dm.
• Use: thrash and death riffs on E–F–Bb, dissonant black metal.
• Common mistakes: building long Locrian progressions: it is used as riff color.

Tritone and chromaticism

• Tritone: an interval of 6 semitones (E–Bb), called "diabolus in musica" by medieval theorists; in metal it is the symbol of tension (Black Sabbath — Black Sabbath: G–G (octave)–Db).
• Chromaticism: power chords rising or falling by half step (E5–F5–F#5–G5), chromatic lines in thrash and death riffs.

Minor pentatonic and blues

• Formula: 1 b3 4 5 b7 / 1 b3 4 b5 5 b7. In E: E G A B D / E G A Bb B D.
• Use: 1970s heavy, groove metal (Pantera), solos.

How to choose

Rule of thumb: keep the tonic on the open string (pedal) and choose the scale based on the note you put right above it (F = Phrygian, F# = Aeolian/Dorian, Bb = Locrian/tritone).

Harmony

Riffs before chords

Metal harmony is based on riffs more than on chords: power chords (root + fifth, possibly the octave; sometimes also the minor third or the diminished fifth), tritone and minor-second intervals, tonic pedals (open string) with passing notes above. With distortion, the power chord generates intermodulation products in the low end that make the sound "thicker".

Modal progressions

• Wikipedia cites the modal progressions I–bVI–bVII and I–bII–I as typical: in a minor key (notation from natural minor) i–VI–VII and i–bII–i.
• Classical V–i cadences only in neoclassical and power metal.
• Slow harmonic rhythm in the epic parts (one chord per bar), fast in the riffs (a chord every eighth note).

Pedal and open string

• "Pedal" riffs: the low open string repeated in palm mute with power chords or notes moving above it (E–E–F–E–E–G: Metallica, Slayer).

Two-guitar harmonies

• Melodies harmonized in diatonic thirds (Iron Maiden, Thin Lizzy) or in fifths/fourths (darker).

Density

• Verses with a single riff; choruses with sustained open chords or continuous strumming; breakdowns with a single rhythmic note.

Voicing

• Power chords on the low strings, octaves, chords with open strings; in modern metal, open chords with the ninth (add9) in the melodic parts and dissonant clusters (black, djent).

Typical progressions

Rhythm and groove

4/4 as the frame, with countless variations: gallop (eighth note + two sixteenth notes, Iron Maiden), double kick in continuous sixteenth notes, skank/thrash beat (kick on the beats and snare on the offbeats), blast beat (a very fast kick–snare alternation, generally from 180 BPM in sixteenth notes upward, often 250–280), half time and breakdowns, odd meters and polyrhythms (prog, djent). Rhythmic precision is extreme: guitars and drums often play in unison and the palm mute has to coincide with the kick. The tempo range goes from about 60 BPM (doom, ballads) to 350 BPM in extreme blasts (Wikipedia data).

Drums

Role

In metal the drums are part of the riff: the kick often plays in unison with the palm-muted guitars, the snare gives the "perceived tempo" (full, half, double), and the cymbals provide energy. The kit is bigger than in rock (double bass drum or double pedal, more toms, China, splash), and cymbal chokes (grabbed with the hand) are characteristic.

Kick

• Classic heavy: 1 and 3 + gallop (x.xx on every quarter note) in the fast parts.
• Double kick in continuous sixteenth notes (steps 1–16 all filled) under snare on 2 and 4: the "wall".
• Unison with the riff: the kick copies the guitar chugs (for example x..x..x...x.x... in the breakdowns).
• Sound: kick with click (beater at 3–8 kHz) to be heard at high speeds; often triggered or replaced by samples.

Snare

• 2 and 4 in midtempo metal; on the offbeats in the skank/thrash beat; alternating with the kick in the blast; on 3 in half time.
• High, even velocity (with triggers); ghost notes are rare (more frequent in prog and groove metal).

Cymbals

• Ride in quarter or eighth notes (bell for accents), China on accents and in breakdowns, crash on every phrase, splash in fills; closed eighth-note hi-hat in midtempo verses.

Interaction with bass and guitars

• Guitars, bass and kick form a single block; the drums leave "air" only where the riff has rests.
• The vocal rarely dictates the rhythm: the drums follow the riff.

Sections

• Intro: clean arpeggio, orchestra or riff with half-time drums.
• Verse: thrash beat or double kick.
• Pre-chorus: half time or toms.
• Chorus: double kick and open cymbals, or a heavy midtempo beat.
• Solo: double kick or gallop.
• Breakdown: half time, syncopated kick in unison, China on the quarter notes.
• Ending: return of the main riff, stop with a choke.

Fills

• Sixteenth-note and sextuplet rolls on the toms, fills with double kick underneath, "cascading" fills toward the crash.

Sounds and programming

• Multi-velocity samples with round robin (Superior Drummer, GGD, Toontrack Metal Foundry; in FL Studio FPC or any drum sampler), kick velocity 110–127 with small variations, snare ghost notes at 20–40.
• The velocities of a real double pedal are not identical: alternate 120/112 for right/left foot.

Typical mistakes

• Kick without click that disappears in the double kick; double kick with long tails that make mud (shorten the samples); blasts too fast for the riff to keep up; no variation in cymbals between sections.

Bass

Sound

4-, 5- or 6-string electric bass, often played with a pick, tuned down like the guitars; a sound that combines a clean sub and a distortion in the mids (bass split).

Role

• Doubles the riff of the guitars (an octave below or in unison) or holds the root under more complex riffs.
• Melodic bass in classic heavy (Steve Harris of Iron Maiden, gallops with the fingers) and in prog (Sean Malone, Steve Di Giorgio).

Relationship with the kick

• Kick and bass play the same hits; the kick takes 50–80 Hz of "punch" and 3–8 kHz of click, the bass 80–200 Hz of body and 700 Hz–2 kHz of "growl".

Notes

• Root, octave, unisons with the riff; chromaticism in thrash riffs; long notes under the blasts in black metal.

Examples

• Iron Maiden — The Trooper (Steve Harris); Metallica — Orion (Cliff Burton); Death — Symbolic (Kelly Conlon).

Harmonic instruments

Layering of rhythm guitars (modern metal)

• Quad tracking: 4 separate performances of the same riff (never copies: you need the micro-differences for width), two per side: L100 + L80 and R100 + R80 (or all four at L100/R100 if you want maximum width).
• Different amps per side or per pair: for example Mesa/Boogie Dual Rectifier + Peavey/EVH 5150 (or their simulations), or the same amp with two different cabinet IRs (Mesa 4x12 with V30 + Marshall 1960 with Greenback). Sound On Sound suggests, for live-recorded guitars, two amps with contrasting/complementary tones panned to the extremes.
• Double vs. quad: double tracking (L100/R100) is more defined and "tight"; quad tracking is bigger but less precise. Thrash and technical death prefer 2 very precise tracks; modern metalcore, deathcore and djent often use 4 tracks or 2 tracks + re-amp.
• Always record the DI: it lets you re-amp and change the sound in the mix.
• Leads and harmonies: in the center or L30/R30 (third harmonies, one per side), with delay and reverb; the rhythm part stays dry.

Typical tunings

The "drop" tunings of the drop D family (drop Db, C, B, Bb, A) all use the same fingerings: power chords with a single finger on the three low strings.

Technique and tone

• Palm mute: the picking hand resting on the strings near the bridge; with distortion it gives the heavy, tight, precise "crunch" that emphasizes the lows.
• Gain: classic with moderate gain and a loud amp; thrash with scooped mids and tight compression; modern with lots of gain but tight (a Tube Screamer in front of the amp to tighten the lows).
• Guitars: high-output humbuckers (EMG 81/85, Seymour Duncan), thin necks, Floyd Rose; 7 and 8 strings in modern metal.

Keyboards and orchestra

• Organ (1970s), synth pads (1980s heavy), orchestra and choirs (symphonic), synths and electronics (industrial, modern metalcore).

Melody and vocals

Vocals

• Clean and high: Rob Halford, Bruce Dickinson, Ronnie James Dio (heavy, power): powerful head voice, vibrato, sustained high notes.
• Raspy/shouted: James Hetfield, Tom Araya (thrash).
• Growl (death): deep guttural voice; scream (black, metalcore): high, hoarse voice; pig squeal (deathcore).
• In metal the vocal is subordinate to the band's sound but must convey an explicit emotion.

Melodies

• Modal (Aeolian, Phrygian, harmonic minor), with broad phrases in the choruses; in extreme verses the vocal is rhythmic and follows the riff.

Backing vocals

• Epic multi-voice choirs (power, symphonic), gang vocals (thrash, metalcore), lyrical choirs (symphonic: soprano + chorus).

Effects

• Clean: plate/hall and delay; harsh: tight doubles, saturation, little reverb.

Instruments

• Two electric guitars (6, 7, 8 strings), rhythm and lead or two rhythm + lead.
• Electric bass with 4–6 strings.
• Drums with double kick (or double pedal), 3–5 toms, ride, 2–4 crashes, China, splash.
• Vocals (clean, growl, scream).
• Keyboards: organ, synth, piano; orchestra and choirs in symphonic; synths and electronics in industrial and modern metalcore.

Drum patterns

Synths and sounds

• Augmented Strings — Orchestral strings: Epic strings for symphonic and intros: legato in octaves, mid-high register, above the guitars (not in the same octave as the power chords).
• Augmented Voices — Choirs: Epic choirs for intros and choruses: male and female 'aah' on long chords.
• B-3 V — Organ: 1970s heavy organ (Deep Purple, Uriah Heep, Rainbow): full drawbars, distortion.
• Jup-8 V — Pad and lead: Supporting synths in 1980s heavy and power metal: wide saw pads, leads with glide.
• Prophet-5 V — Modern synths: Arpeggios and pads in metalcore and modern alternative metal.
• Mellotron V — Vintage choirs and strings: Dark intros and 1970s atmospheres (doom, stoner).

Song structure

Typical form (4:00–7:00)

Mixing and mastering

Sonic goal

Power and definition together: a wide wall of guitars, drums that cut through the wall (kick with click, bright snare), bass that adds weight without mud, intelligible vocal. Each subgenre has a different ideal (from the natural sound of 1980s heavy to the hyper-produced sound of metalcore), but the principle is the same: separate in frequency instruments that are all playing at the same time. References: Metallica — Metallica (1991), Gojira — Magma (2016), Architects — Holy Hell (2018).

Kick

• EQ: HP 30–35 Hz; punch at 50–70 Hz (+3 dB, Q 1.5); heavy cut of the boxiness at 250–500 Hz (−6/−8 dB, Q 2); click at 3–5 kHz (classic) or 6–8 kHz (extreme metal), +4/+6 dB.
• Compression: 4:1–8:1, attack 5–15 ms, release 50 ms, 4–6 dB; often replaced/supported by samples (triggers) with a gate to shorten the tail.
• Saturation/clip: soft clipper (Fruity Soft Clipper) for 1–2 dB on the peaks.

Snare

• EQ: HP 100 Hz; body 180–250 Hz (+3 dB); cut 400–800 Hz (−3 dB); crack 4–6 kHz (+4 dB); air 10–12 kHz.
• Compression: 1176 4:1, attack 3–5 ms, 6 dB; parallel; reinforcement sample (blend 30–60%).
• Reverb: room or plate 0.8–1.5 s, pre-delay 10–20 ms, on the snare only (not on the guitars).

Toms and cymbals

• Toms: gate or editing, +4 dB at 80–120 Hz, −5 dB at 400 Hz, attack at 4 kHz.
• Overheads: HP 300–500 Hz (cymbals shouldn't carry lows), −2/−3 dB at 3–4 kHz if harsh; China with de-esser.
• Drum bus: 4:1, 3–4 dB; compressed parallel (8–10 dB) at 20–30%.

Bass

• Bass split: (1) clean sub with LP at 150–250 Hz, compressed 4–6 dB; (2) distorted (SansAmp, Darkglass, Fruity Blood Overdrive, amp sim) with HP at 200–300 Hz, +3 dB at 800 Hz–1.5 kHz (growl), LP 5–6 kHz.
• Total compression 8–10 dB: metal bass is very even. Mono.

Rhythm guitars

• Layering: see harmonic instruments (2 or 4 tracks L/R).
• EQ: HP 80–100 Hz (higher for low tunings: up to 60–70 Hz on drop A with a well-defined bass); cut 200–400 Hz (−2/−4 dB, "mud"); presence 2–4 kHz to control (if harsh, −2 dB at 2.5–3.5 kHz); cut the "fizz" at 6–8 kHz; LP 10–12 kHz.
• Dynamic EQ at 100–200 Hz (reduces the "boom" of palm mutes) and sidechain from the kick (−2/−3 dB at 60–120 Hz) to leave room for the punch.
• Gate before the amp (Fruity Limiter in gate mode, NS-2) for clean stops.
• No reverb on the rhythm parts.

Lead guitars

• Center (or harmonies L30/R30), +2 dB at 1–1.5 kHz, 1/4 or dotted 1/8 delay (feedback 20–30%, −15 dB), hall or plate 1.5–2 s.

Lead vocal

• Clean: EQ (HP 100 Hz, −3 dB at 300 Hz, +3 dB at 3–4 kHz) → 1176 (6 dB) → LA-2A (3 dB) → de-esser → plate/hall + delay.
• Growl/scream: HP 120–150 Hz, −3 dB at 400–500 Hz, +3 dB at 1.5–3 kHz, heavy compression (10 dB in two stages), light saturation, tight doubles (L10/R10), little reverb (short room).
• Automation of the level word by word: the vocal must sit on top of the wall without being "pop".

Backing vocals and FX

• Epic backing vocals with long hall; gang vocals with room; FX (risers, impacts) only in modern metal.

Buses and groups

• Guitar bus with light compression (1–2 dB) and a dynamic EQ; drum bus; vocal bus. Glue on the mix 2:1, 1–2 dB.

Sidechain

• Guitars and distorted bass: dynamic EQ sidechained from the kick (60–120 Hz, −2/−3 dB, attack 1 ms, release 50 ms).
• Guitars: −1/−2 dB at 2–4 kHz sidechained from the vocal.

Master

• Chain: EQ → bus compressor (2:1, attack 30 ms, 1–2 dB) → clipper → limiter.
• Target: classic heavy −10/−8 LUFS integrated; modern metal −8/−6 LUFS (short-term in the choruses −6/−5); true peak −1 dBTP (−2 dBTP above −14 LUFS, per Spotify's guidelines, which normalizes to −14 LUFS).
• Case study: Metallica's Death Magnetic (2008) was criticized for excessive compression and audible distortion (mastering engineer Ted Jensen said the mixes arrived "already brick-walled"); the versions without final compression that circulated from the video game Guitar Hero showed the difference.

Common mistakes

• Too much gain (the guitars turn into noise); mud at 200–400 Hz; inaudible bass; kick that disappears in the fast parts; a squashed, distorted master; vocal too low or too "pop".

Reference tracks for the mix

• Black Sabbath — Paranoid (1970); Iron Maiden — The Trooper (1983); Metallica — Enter Sandman (1991); Pantera — Walk (1992); Gojira — Stranded (2016); Architects — Doomsday (2017).

Reference listening

• Black Sabbath — Paranoid (1970)
• Judas Priest — Breaking the Law (1980)
• Iron Maiden — The Trooper (1983)
• Metallica — Master of Puppets (1986)
• Slayer — Raining Blood (1986)
• Metallica — Enter Sandman (1991)
• Pantera — Walk (1992)
• Slipknot — Duality (2004)
• Gojira — Stranded (2016)