Metal’s ‘devil’ interval was once banned in theory books
Heavy metal grew from late-1960s blues-rock and psychedelia into a monument of distortion, solos, and sheer volume. One of its favourite intervals—the tritone, three whole tones spanning something like C to F-sharp—medieval theorists nicknamed diabolus in musica, the devil in music. The genre turned that old dread into a signature tension.
British pioneers Led Zeppelin, Black Sabbath, and Deep Purple all formed in 1968, drawing thick tones from blues rock, psychedelic rock, and acid rock. American acts such as Alice Cooper, Kiss, Aerosmith, and Van Halen later opened more accessible lanes. Mid-1970s Judas Priest shed much blues influence; Motörhead brought punk speed. The late-1970s new wave of British heavy metal—Iron Maiden, Saxon—followed. Nineteen-eighties glam (Mötley Crüe, Quiet Riot) shared the decade with thrash breakthroughs by Metallica, Slayer, Megadeth, and Anthrax, while death and black metal stayed largely underground.
Sonically, the electric guitar is central: high volume plus heavy fuzz, palm-muted rhythm crunch, and at least one solo in most classic songs (nu metal and grindcore often skip solos). Bass underpins the weight—Cliff Burton’s early Metallica solos and Lemmy’s overdriven chords are oft-cited extremes—and drums chase speed, power, and precision, including cymbal chokes and, in extreme styles, double-kicks and blast beats. Tempos now range from ballad paces near sixty beats per minute to blast beats near 350. Power chords, often a perfect fifth with optional octave doubling, thicken under distortion.
Harmony leans on Aeolian and Phrygian modal colours, pedal points, chromatic motion, and that tritone bite, alongside blues and pentatonic residue. Critic Jon Pareles called metal hard rock’s less syncopated, more showy, more forceful breed. Sociologist Deena Weinstein treats loudness itself as metal’s melodic equivalent—an “onslaught” meant to sweep listeners in. Robert Walser argues classical study among guitarists reshaped metal virtuosity from the start. Until at least the mid-1980s performers were almost all male; by the 2010s women were more visible, especially as leads in power and symphonic acts such as Nightwish and Within Temptation.
Source: Heavy metal music
