Mikael Akerfeldt has already demonstrated his ability to alternate pitch regulary when he growls. For Death Metal, the norm is to harmonize the growls with the guitars. This sounds brutal when done correctly, but how far could you take growl vocals? Instead of growling the same note and alternating pitch occasionally, imagine if one could sing melodies with growl vocals. This would eliminate the monotonous element of death metal. Its already been done with related vocal styles in other metal genres, but I can't name a band that has melodic death metal vocals.