Thrash
Thrash Metal is a sub-genre of rock that focused on an aggressive, "underground" sound. This meant heavily distorted guitars, screamed vocals, and up-tempo songs with non-stop drumming. Guitars typically played riffs, rarely playing sustained chords. Riffs took inspiration from both blues and classical compositions. Fast guitar solos were also prominent. Rather than use rich harmonies for chorus sections, thrash typically built tension using rhythm drops, vocal-guitar point-counterpoint, or tempo shifts. Song structures often took experimental routes, sometimes omitting choruses altogether. Popular thrash artists are Metallica, Megadeth, Pantera, and Slayer.
Contents
Riff-based Tonality
Thrash artists rarely played even basic triad chords, instead focusing on riffs (outside of clean intros or interludes). A riff at its most basic level is simply a repeating single-note melody line. While rock music generally expanded upon this, thrash took it to the next level. Given that heavy distortion tends to compress the sound, using conventional dynamics by altering picking strength provided little tonal difference. Additionally, thrash's absurdly fast tempos made it difficult to apply contrasting picking strength during a riff. Seeking contrast for the notes inside riffs, artists expanded some notes as power chords while palm muting others.
Scale
Tonality mostly came from the scale the riffs were played in, which was typically a natural minor or a blues or a combination of the two. At times it may even become completely chromatic. Many songs revolve around the low open E, using an E minor or E blues scale (or Eb if tuned down a half step). It could also be or modulate to A (or Ab).
Pedal Points
A pedal point is a note that is held constant or consistently reinforced over a passage of changing harmonic content. For thrash metal, this typically meant low E or A string palm mutes being used as the backbone of a riff, with other notes playing off this tone.
D-------------9-----7-/9--------9-----7-/9-- A-------------7-----5-/7--------7-----5-/7-- E-0--0--0--0-----0--------0--0-----0-------- p p p p p p p p D-------------5-----5-/4--------5-----5-/4-- A-------------3-----3-/2--------3-----3-/2-- E-0--0--0--0-----0--------0--0-----0-------- p p p p p p p p
Sometimes thrash artists would change the pedal point but continue playing the same riff otherwise, altering the feel of the riff.
D-------------9-----7-/9--------9-----7-/9-- A-0--0--0--0--7--0--5-/7--0--0--7--0--5-/7-- E------------------------------------------- p p p p p p p p D-------------5-----5-/4--------5-----5-/4-- A-0--0--0--0--3--0--3-/2--0--0--3--0--3-/2-- E------------------------------------------- p p p p p p p p
Spider Fingering
With thrash riffs often playing consecutive power chords with different root notes, some players noticed they could use alternating index/ring and middle/pinky fingers to finger the chords, achieving greater economy of motion (allowing them to play even faster) and avoiding any scratchy sounds from sliding positions up and down between chords. This is called spider fingering.
D-------4--3-----2--3----- A-2--3--2--1--4--0--1--2-- E-0--1--------2--------0-- m r p r p m r m o i m i m o i o
Black Notes (Metal's Blue Notes)
Blues used minor 3rds and 7ths and diminished 5ths for a distressed sound. Thrash similarly would substitute in minor 2nds and diminished 5ths into a minor scale to get an evil or doom-inspired sound. Rather than simply using these notes in passing, they would often be accented in riffs. Here's an example in Em.
m2 d5 m2 m2
D---------------------3--------------------
A-2-------3-----------1-----3-----3---2----
E-0---0-0-1---0-0-3p0-----0-1---0-1---0----
p p p p p p
Shred
With thrash already concerned with speed and shredding guitar solos already popular in the Hair Metal scene, thrash had to take things even faster and flashier. Song structures were adjusted to incorporate more solos and/or with longer length. Players began to explore special techniques to get even faster, such as sweeping and tapping. They also experimented with the recent development of floating bridges and the insane whammy bar techniques that it brought.
Downpicked Palm Mutes
Although thrash was often focused on speed, many prefered to downpick all palm mutes to get them more of a repetitive and percussive sound. This didn't mean that tempos were lowered, but that large amounts of practice went into getting rhythmically-consistent, fast, consecutively-downpicked notes. This requirement was often relaxed for unmuted notes or subdivisions of the normal rhythm.
d d d d d d d d d u d d d d u d u E-|0---0---0---0---0---0---0---0--|0-0-0---0---0---6---5---3---5---| p p p p p p p p p p p p p
Guitar Tone
Guitar tone in thrash metal is typically heavily distorted, reducing the instrument's dynamic range. This allows palm mutes to have similar dynamics to unmuted notes. While many modern amplifiers feature distortion that allows saturated distortion without becoming "farty" in the lower frequencies, earlier thrash bands used amplifiers that could get fuzzy or muddy when pushed to extreme distortion, particularly on palm mutes. This reduces the clarity of notes' fundamental frequencies as well as reducing the audibility of players' pick attack. To counter this, boost/overdrive pedals or pre-EQ was used to "tighten" the distortion tone, focusing the distortion on the midrange and treble frequencies but retaining clarity of the fundamental frequency for each note. Thus, listeners could hear the individual notes being played, even during fast passages with heavy distortion.
Reverb on distorted rhythm guitars is used subtly if at all, delivering a very "raw" guitar sound. Rather than rely on reverb to fill sparse passages, players filled the space by playing quickly and rarely pausing or sustaining notes/chords.
Clean guitar tones were often used for intro sections or bridges. These generally used pristine clean tones with little to no distortion, offering extreme contrast with distorted tones. This allowed compositions to use minor and suspended chords with their qualities clearly heard, as well as bearing more similarity to classical-era guitar tones.