Agalloch are grounded in the dark metal genre, but i personally think they have nothing to do with the other bands from the same category, that’s because they chose to experiment and not to be limited to a certain label/sub-genre, that makes them unique. Agalloch deliver the coldest type of music your ears would ever hear, with influences of the following genres:
folk/neo folk, gothic doom, rock , avant-garde, dark ambient, atmospheric and black metal music…
What makes them so different is the fact that they use the most simple structures and melodies followed by emotion stimulating effects that take you on a trip through the darkest Scandinavian forest eventhough the band probably resides in some fancy apartment in Portland, Oregon.
What makes Agalloch mostly unique, is the progressive structure of their songs and albums, no matter how simple they sound, they are progressive! Acoustic parts, growling, wind sounds,pianos, pipe organs, random babbling in some songs, distortion, violins and much more.
Update
For those who wish to listen to random songs by Agalloch i suggest the following (note that hearing one track from the album wouldn’t be enough for you to understand and appreciate it or the band):
Falling snow from Ashes against the grain (2006)
The melancholy Spirit from Pale folklore (1999)
The misshapen steed from Pale folklore (1999)
Tomorrow will never come from Tomorrow will never come (2003 EP)