As the first three albums had been rather, hm, culty Black Metal, the predecessor "Blood, Fire, Death" showed a transgression into slightly different terrain. "Hammerheart" then had been (most probably) the first ever Viking Metal-album in 1989, and with this a pioneer of this style (which in itself isn't a real style in fact).
The production still sounds a bit daring, not only by today's standards, but it just adds to the appeal and character of the album. Musically the songs are mostly in the slow-paced tempo, emanating a kind of epicism that would fit any wide-screen movie about the epoch of Vikings. You'll find lots of melodies here, suiting the pathetic (the positive meaning of this word!) lyrics, try to picture "Braveheart" on Vikings and you'll roughly have it.
Yet who thinks that the more extensive use of melodies and the slower tempo means a dilution of heaviness, think again, the songs still are heavy, but not drawing it from speed or brutality, but from the lava-like viscosity of the riffs. Just listen to "Baptised In Fire And Ice" and you know what I mean, melody and epic atmosphere always in the fore. With "Song To Hall Up High" they even have a song that you could call balladesque in its melodies and you really have to have heard the masterpiece "One Rode To Asa Bay" for yourself to be able to grasp its majesty.
Quorthon's clear voice (yes, no growls or shrieks) doesn't always sound completely secure, but that also just adds to the character of this album.