Grindcore evolved as a blend of thrash metal, thrashcore and hardcore punk. The name derives from the fact that grind is a British term for thrash; that term was appended to -core from hardcore. Grindcore relies on standard hardcore punk instrumentation: electric guitar, bass and drums. However, grindcore alters the usual practices of metal or rock music in regard to song structure and tone. The vocal style is "ranging from high-pitched shrieks to low, throat-shredding growls and barks." In some cases, no clear lyrics exist. Vocals may be used as merely an added sound effect, a common practice with bands such as the experimental Naked City.
A characteristic of some grindcore songs is the "microsong," lasting only a few seconds. In 2001, the Guinness Book of World Records awarded Brutal Truth the record for "Shortest Music Video" for 1994's "Collateral Damage" (the song lasts four seconds). In 2007, the video for the Napalm Death song "You Suffer" set a new "Shortest Music Video" record: 1.3 seconds. Beyond the microsong, it is characteristic of grindcore to have short songs in general; for example, Carcass' debut album Reek of Putrefaction (1988) consists of 22 tracks with an average length of 1 minute and 48 seconds. It is also not uncommon for grindcore albums to be very short when compared to other genres, usually consisting of a large track list but having a total length of only 15 to 20 minutes.
Many grindcore groups experiment with down-tuned guitars. While the vinyl A-side of Napalm Death's debut, 1987's Scum, is set to standard tuning, on side B, the guitars are tuned down 2½ steps. Their second album From Enslavement to Obliteration and the Mentally Murdered EP were tuned to C♯. Harmony Corruption, their third full-length album, was tuned up to a D. Bolt Thrower went further, dropping 3½ steps down (A). Bass is tuned low as well, and is often distorted.
The blast beat is a drum beat characteristic of grindcore in all its forms, although its usage predates the genre itself, as it is native to jazz. In Adam MacGregor's definition, "the blast-beat generally comprises a repeated, sixteenth-note figure played at a very fast tempo, and divided uniformly among the kick drum, snare and ride, crash, or hi-hat cymbal." Blast beats have been described as "maniacal percussive explosions, less about rhythm per second than sheer sonic violence." Napalm Death coined the term, though this style of drumming had previously been practiced by others. Daniel Ekeroth argues that the blast beat was first performed by the Swedish group Asocial on their 1982 demo. Dirty Rotten Imbeciles ("No Sense"), Stormtroopers of Death ("Milk"), Sarcófago ("Satanas"), Sepultura ("Antichrist"), and Repulsion also included the technique prior to Napalm Death's emergence.
Grindcore lyrics are typically provocative. A number of grindcore musicians are committed to political and ethical causes, generally leaning towards the far left in connection to grindcore's punk roots. For example, Napalm Death's songs address a variety of anarchist concerns, in the tradition of anarcho-punk. These themes include anti-racism, feminism, anti-militarism, and anti-capitalism. Other grindcore groups, such as Cattle Decapitation and Carcass, have expressed disgust with human behavior, animal abuse, and are, in some cases, vegetarians or vegans. Carcass' work in particular is often identified as the origin of the goregrind style, which is devoted to "bodily" themes. Groups that shift their bodily focus to sexual matters, such as Gut and the Meat Shits, are sometimes referred to as pornogrind. Seth Putnam's lyrics are notorious for their black comedy, while The Locust tend toward satirical collage, indebted to William S. Burroughs' cut-up method.