i've been listening to a lot of Atheist, Cynic & Spiral Architect this week, bands i thought were quite jazzy, but upon playing some Spiral Architect for a friend of mine who has a music degree, he mentioned that the only thing jazzy about them (or certainly about "Moving Spirit") was the bass. he did explain himself, satisfactorily so, and me not knowing my jazz, accepted his word. i didnt, however, get a chance to ask him what gave those bands their unique sound, if not jazz.

there's a chance that it was just what he heard that wasnt particularly jazzy, because i only got to play him a bit, but regardless, my questions are these:

if you know these bands, what is that element that set them apart from other metal bands, soundwise, if not jazz? or is it jazz, as i thought originally?

how would one achieve a similar sound, from a musical standpoint (scales, etc)?
not that i want to rip them off, but i would like to apply their musical approach to some of my work.