How do you create death metal riffs,is it just play till you got something or is it based on theory or what??!!??

I don't understand anything of any scale,I practised them quite a lot,but I don't know what I'm doing.
Can you use these scales to get something like Obituary,Monstrosity,Unleashed,Pestilence etc??

When I see a tab,I try to get some logica of it,but it seems it doesn't.

Unleashed for example,''where no life dwells'' album,can someone explain a little bit how they could get composing these songs??

I have no band,I just play guitar on my own,so it's very hard to get some riffs together by just play something till you get something..
How can you create some timing in your riffs so everything will not sound the same??

Thanx!!

this is something everyone who has ever written a riff has struggled with before. the bands you mentioned (kickass old school dm! good choices!!) all use chords to create their riffs, simple root and fifth shapes. those are hard to write and make catchy or have much of a melody, but to make a really heavy main riff or breakdown (chopped in half ) they are perfect. death metal RIFFS are best shown by something like malevolent creation or cannibal corpse...the early stuff. almost no chords just a series of notes trem picked that create a melody

timing , like you said, is essential in variation. i have a very hard time with that and i can feel your pain on it

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There are good threads to look at in the theory forum and maybe some other threads in this one to help you with this.

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