The metal genre gets to a point where it becomes less of any form of rhythm and more of the stereotypical beating and flailing your hands and arms over your instruments while the vocalist screams things he can't understand.
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Technical death is anything but. Although vocals do become unintelligible in many of the sub-genres. It really depends on th e vocalist. Some like Anders from In Flames and Björn from Soilwork have pretty understandable harsh vocals.