The roots of metal are found in the pioneering work of the band Black Sabbath. Sabbath initiated a new style of rock music in the early 1970s with heavy power chords and guitar riffs and dark edgy lyrics. Sabbath's music was influential on numerous metal bands from Iron Maiden and Judas Priest to heavier metal bands like Slayer, Metallica, and Motorhead. Thrash metal is a subdivision of metal and it is characterized by blistering speed and very aggressive playing. Writing thrash metal songs requires diligent practice and the right equipment.
Set up the guitar and amplifier for a thrash metal sound. Metal guitarists use heavy strings and lots of distortion. A trick many metal guitarists use, a lesson learned from Sabbath, is to tune the guitar a whole step or even two whole steps. A guitar in standard tuning is tuned E A D G B E. When it is tuned two whole steps down it is tuned C F B-flat E-flat G C. The low tuning provides a much heavier sound. You also need an amplifier with distortion or a distortion pedal. Set the gain and treble at 10 and the bass at 2 or 3.
Develop speed and dexterity by practicing pentatonic, minor, and major scales with a metronome. Thrash metal is characterized by blistering speed and accuracy. This requires chops and this takes practice. Practicing scales with a metronome is the best way to increase speed and accuracy. Play all the scales in a series with the metronome. Set the metronome at a slow speed and play the scale with quarter notes, one note per beat; eighth notes, two notes per beat; triplets, three notes per beat; and sixteenth notes, four notes per beat. Increase the speed of the metronome once you are able to play through the series. Keep increasing the speed. Developing your guitar chops gives you a wealth of resources for songwriting ideas.
Start with a power riff. Thrash metal songs, and metal in general, are built around guitar riffs and power chords. The riffs are played on the lower E, A, and D strings. Thrash metal is often characterized by very fast and intricate riffs but this is not always the case. Listen to different bands for inspiration. A very good online resource is guitarmasterclass.net. There are examples of numerous thrash metal riffs to listen to and learn from. The song will be built around the guitar riff in combination with the bass and drums. One nifty device for songwriting is the Boss RC 2 Loop Station. It allows you to record eleven different tracks that are each sixteen minutes long. You can layer multiple guitar parts on each track. There is also drum accompaniment provided. The drum tempo may be increased or decreased. Many riff ideas come from jamming with a band. The Loop Station provides you with a band and stores the ideas you come up with.
Pick a theme for the lyrics. Nothing is off limits for lyrics in thrash metal but they do tend to make some sort of social commentary. Possible themes may be the abuse of power, exploitation, addiction, murder, fantasy and the dark side of life. Match the lyrical content to the music you have written. One strategy often used is to simply sing nonsense lyrics as you play the song. This is done to find a vocal melody line and rhythm. Once a good vocal melody is found then you can go back and carefully construct the lyrics.
Create a structure for the song. Once the main riff and the theme for the song have been developed, it is time to fine tune it and turn it into an actual song. Thrash metal songs follow the typical song structure used in popular music. This involves verses and a chorus or bridge that is repeated throughout the song. The lyrical content unfolds within this framework. The bridge often uses a different chord combination that separates it from the verses. If the song and the main riff is in the key of E , the bridge can utilize the IV and V chords which are A and B7. The V chord logically moves back towards the I or E chord and forms a natural resolution.
Polish the song. The final step that adds a professional touch to a song is a well-crafted arrangement. This involves working out the intro, deciding where the solos are, developing dynamics within the song, and working out an ending.