Dark psytrance (also killer psytrance, dark psy, forest trance, horror trance, horror psy, psycore, or black trance) is a darker, faster and more distorted form of psychedelic trance music, with tempo ranges usually from 145 to 180 BPM, but reaches +220 BPM. It is originated in Russia and has expanded to other countries worldwide.
Dark psytrance generally does not use vocals, though sampling is common, with speech and other kind of samples usually being taken from different kind of movies (especially horror or sci-fi movies), or from cartoons such as Futurama, South Park, etc.
The atmosphere and theme of the tracks very loosely resembles those from genres such as dark ambient, musique concrète, darkcore, power noise and industrial music. At times atmospheric and "deep" sounds are used to create a haunting and Gothic effect such as those used by Xenomorph, Psychoz, Mooname, Parasense and Kemic-Al. On the other side there is high-tech darkpsy, with a higher BPM (160-220), and powerful baselines, without a gothic or horror atmosphere. Other artists such as Baphomet Engine and Whicked Hayo add in metal samples to darken the music, linking it to industrial metal.
Recently, some artists who previously were dark psytrance artists, such as N3XU5, Darkpsy, Kalilaskov AS and Fungus Funk, have started producing a more melodic, South African-like sound, whilst some others are starting to experiment with using melodies and morning trance elements in dark psy like Deja Vu Fabrique (Zolod from Parasense), and C-P-C. However, the whole electronic music scene has evolved, and most artists indulge in experiments to produce many varied genres such Psychedelic Chillout, Progressive Psytrance, Dubstep, Psychedelic Breaks, etc.
The beginning of the new decade has seen a tremendous rise in the popularity of high BPM music. With tracks going as fast 180-190, this type of music is generally associated with horror samples and evil and devilish atmospheric synths.
Forest trance is characterized by more organic sounds, and is generally a bit slower (140-155 BPM) than other types of dark psytrance. Notable names in this subgenre are Atriohm, Derango, Megalopsy, Krussedul and Purosurpo.
Psycore on the other hand is distinguised by its higher tempo (170-200 BPM) and many breaks. Some artists that produce this type of music are Cosmo, Highko and their collaborative project Highcosmos, and Furious.
...more info at http://en.wikipedia.org/wiki/Dark_psytrance