Poster: Hank @ Thu Jun 02, 2011 8:15 am
For the curious :
Grindcore songs are usually short, warpspeed, unrelenting blasts of aggression. Songs less than one minute long are common. The guitar riffs, complex as they may be, usually just sound like a mass of thrashing noise. The drums are responsible for most of the sonic texture, with tight fills punctuating the "blast beat" style sixteenth-note onslaught. On-a-dime start / stop dynamics characterize the performances. Lyrical topics are often more focused on socioeconomic evils like oppression, fascism / sheepism, environmental collapse, alienation, and general depravity than the slasher-film-style gore that characterizes death metal (though militant vegetarian-grind exponents like Carcass and Cattle Decapitation use extreme gore as a way to illustrate the horrors of the meat industry). Vocals are most often done in the "cookie monster" grunt, though a rasping style is also heard. Grindcore is heavily influenced by hardcore punk in its short-sharp-unornamented aesthetic.
Death metal songs share grind's brutality, but are usually more riff-centric, with more complex (and distinguishable) guitar patterns, longer songs, and even guitar and drum solos (which you'll rarely hear in grindcore). Shifting, asymmetrical song structures are common. Vocals are "cookie monster" or delivered in a throaty roar (sometimes, black-metal style rasps are heard). Lyrics tend to focus on blow-by-blow, near-medical accounts of gory violence, Satanism / anti-Christian / demonic stuff (which is almost never addressed in grind), and similar dire topics. Aesthetically, death metal is closely aligned with traditional 70s metal tropes inherited from Black Sabbath.
There are a lot of variations within the genres. For example, grindcore that uses drum machines to achieve crazy tempos and inhuman precision, as seen with the brilliant Agoraphobic Nosebleed, is often called "powerviolence;" bands that mix death metal growling and aggression with modern-rock influenced riffing and tempo have been called "death 'n' roll," which sobriquet is often applied to Entombed.
There's a lot more to it, but that's kind of the two-minute overview.