Post-Rock is a very hard-to-define genre. Generally, it's a style that needs to be heard to understand. While the genre might be associated with long compositions with crescendos, many post-rock bands, especially from the "first wave" write relatively short songs. Most commonly defined as a band that uses traditional rock instruments to play non-traditional rock music, whether it be modern classical, ambient, noise, or so on, though there are occasional exceptions

Post-Rock has a very confusing history. Some people credit the Velvet Underground for starting it with songs like "Heroin" which started off extremely quiet and ended in droney, massive climax. Other sources give credit to the "Krautrock" movement of The Sixties and The '70s. Another possible Ur-Example is King Crimson's slowly unfolding song "Starless", which contains a lengthy, Bolero Effect-laden instrumental passage typical of the genre, while others point to the works of Public Image Ltd.. All sources seem to agree that the movement "officially" started either in 1991, when Slint released their album Spiderland and Talk Talk released Laughing Stock, or in 1988, when Talk Talk relased Spirit of Eden. All three albums are considered classics and are extremely influential. The term "post-rock" itself is generally considered to have been introduced as a descriptor for music of this genre in a review of Bark Psychosis' 1994 album Hex by music journalist Simon Reynolds which appeared in Mojo in March of that year, although Reynolds claims to have used the term before that review. note  Reynolds clarified the term in an article for The Wire published later that year, describing it as music "using rock instrumentation for non-rock purposes, using guitars as facilitators of timbre and textures rather than riffs and power chords."

For the first few years many music enthusiasts had trouble differentiating this and the genre of Slowcore. This is because Slint were heavily influenced by Codeine, often considered the first Slowcore band. For awhile the droney sounds from the two got many Slowcore bands mislabeled as Post-Rock and vice versa. Another genre which Post-Rock is often confused with (and, indeed, does overlap with in some cases) is Space Rock, which was an influence on it, but which has a somewhat different (read: drug-oriented) focus.

Throughout the The '90s bands such as Cul de Sac, Tortoise, Labradford, Bowery Electric and Stars of the Lid helped mold the genre into what it resembles now. The movement sparked mainly from three different cities with their own separate scenes: Chicago, Glasgow, and Montreal.

Then, in the 2000's bands such as Mogwai, Godspeed You! Black Emperor, and Explosions In The Sky helped expand the genre even more. Then, a number of Sludge Metal bands started picking up on the genre, resulting in "post-metal" or "atmospheric sludge". Since then, the underground has been littered with Post-Rock bands.

The "big 4" of post rock are, generally, considered to be Explosions In The Sky, Sigur Ros, Godspeed You! Black Emperor, and Mogwai.

Bands that are generally considered to be post-rock (post-metal included):

It's worth noting that most of the non-orchestral tracks on the Death Note soundtrack could be considered post-rock. The early works of Mono seem to have been particularly influential on them.