I don't listen to a lot of demos. Usually the production quality is not terribly great, or the songs are rough. However, I do find them to be an interesting look at the early stages of a band.
Here are three demos from Vomepotro, a brutal death/slam death metal band from Brazil.
PRESSED CORPSE (1996)
This is the very first recording from Vomepotro and it is clear they were not really sure what they were doing. The sound is raw and sounds a little weird because it is missing a lot of distortion. The guitar riffs just sound a little off. The band also throws in two covers of Cannibal Corpse's "I Cum Blood" and Slayer's "Angel of Death". Interesting, but the band has not fully emerged yet.
THE PUTRID ODOR (1998)
A slightly longer recording this time around, this one is more like an EP than a demo. Except the production values still are not really that good. The band has incorporated a little bit more of their later defining characteristics into the music. Slamming riffs and a heavy muddy sound have emerged. The vocals have become much more guttural as well. This is a definite step forward for Vomepotro.
This is the most polished demo from the group, though it was still several years before the band's first full-length. The band has really discovered their sound on this one and that sound is a mix between Devourment and Cannibal Corpse. It is a shorter demo, which is disappointing given the fact that it probably has the best production and best songs of the three I have reviewed here.