In the beginning of the song Varg does a double bass part on the drums. Listen to it. It has 2 different pitches. I've always wondered how he did that. Does he just have 2 different bass drums tuned different?

20 views and no replies... Now I just feel stupid....

Having 2 differently tuned bass drums is a possibility. Another possibility is that he was using a double pedal, but the impact with one foot may have not been as forceful as the impact of the other foot, which would create that uneven sound. This sort of thing happens a lot, which is why many drummers trigger the bass drum.