 Besides Bathory , Enslaved , and Burzum , several other artists are credited as pioneers of the style . The original bassist for Emperor , Håvard Ellefsen , also known as Mortiis , was according to AllMusic , " an indispensable force in the genesis of Norway 's epic Viking metal sound . " Despite Ellefsen 's short tenure in the band , it was his musical interests that catalyzed the band to mix chaotic black metal with synthesizer melodies based on Norwegian folk music . 
