The foundation blast beat that all other blast beats arise from is simply continuous 16th notes with the hands on the ride and snare and the same on the double bass drum peddles. This exact beat however, is one of the lesser played blast beats in death metal. The many variations that arise from this beat have their own place in the music. There are beats more common for verses and others that are more common for choruses. For example a lot of drummers bring the two hands into 8th note unison between a cymbal and the snare for verses and then later split it up again for choruses and bridges. Choosing when to play the 8th note snare beat on the beat and when to play it off the beat is a choice made according to the guitar riff. I’d call the off beat (or ‘oom-pa’ beat) more of a thrash thing (as heard in Slayer) and the on beat snare thing more of a black metal thing (as heard in a lot of power metal like Trivium). How and when players decide to play on or off is what makes their sound unique. George Kollias of Nile revolutionised the blast beat by leaving out the left foot part of the double peddle 16ths and the right hand on the ride cymbal and learnt to place crashes at various points with the now available right hand.
The blast beat as opposed to a pure thrash beat is different in that it ‘over plays’ the riff it’s behind. Where guitars play 8th notes in death metal, the drummer usually plays 8th notes on one part (like the hi hat) and 16th notes on another part (usually the bass drum). Where as in “speed metal” or “hardcore” or even hard rock the drummer would just play 8th notes on one part (or between two parts of the kit) and not double up on the bass drum and even play a lesser part again on top of that (like crotchets on a cymbal). Of course we can only generalise about the difference between death metal and thrash metal. The cross overs are countless, and with bands like Shadows Fall playing blast beats it’s impossible to draw the line these days. Slipknot is a great example of diversity, they have wide ranging metal beats from blasting to Nu grooving and even hard rock (and soft rock these days). How diverse a drummer plays beats in a metal band is also another aspect that makes metal drummer unique. How we rank metal genres from fastest to slowest (or more subdivisions to less) is beyond me.
How blast beats are actually played is as long a journey as any musical embankment. All accomplished death metal drummers have extreme technical ability and endurance. The single stroke roll for the hands, feet and between any combinations of the four limbs is the basis of all blast beats. In my experience, playing a single stroke roll with one hand on the ride and another on the snare is harder to play clearly than just playing both on the snare. A lot of death metal drummers will change their type of blast beat from fast to slow to fast and intersperse fills in order to “rest” between the really fast blast beats. For example they might play a 16th note blast between the ride and snare, but then play a fill at the end of the bar and come out into a more ‘thrash’ like beat for a while. Playing a single stroke roll around the kit as a fill is much more forgiving to dropping notes or being a little behind that playing a blast beat. Also, a lot of drummers will mix up the difference between playing fast on the feet and fast on the hands. For a few bars they may play 16ths on the double peddle and 18ths on the hands, then 16ths on the hands and crotchets on the bass drum. There is no doubt though that death metal drummers have massive chops and a great way around the kit. I also am fascinated about the art of blast beats and the many various components that make up what metal is.