The term techno has been used for many kinds of electronic music. Here, it is reserved for the abstract variation on House . Whereas house grooves smoothly, techno kicks furiously. `Techno is a harder edge driven dance music that has the same rhythmic patterns as other house genres but uses a harder synthesizer and a harder sample' (Hosh Gureli), featuring mechanical beats and found sounds that range from apocalyptic sirens to sampled TV and movie dialogue. It was founded in Detroit in the early 80's.

Like House, the original Techno is characterized by the four quarter bass drum: 1 2 3 4. It is somewhat faster than House (126-130 BPM) and does not always contain the disco handclap. Listen to the Sample Lots of creative variations on this theme are made, ranging from the intensely hard percussive sounds made mostly of white noise to the disco sounds that were around in the seventies and the undefined beats and atmospheric chill-out. The speed varies from 0 to 70 bpm in Ambient to 140 in Trance and to 220 bpm in the Hardcore.
Around 1986, there was a scene in Detroit - the city of Motown and P-funk - which made a futuristic kind of music. DJ's played their own music in clubs. It was other music then; now it sounds familiar. The experts say it is a fusion of American P-funk and European synthesizer music (New Order and Kraftwerk). However, the revolutionary thing in Detroit Techno is the layering of rhythms, almost polyrhythmic. Although it is not formal polyrhythmic as in African tribal percussion music: Detroit Techno is highly syncopated and often features triplets over quarter notes. In e.g. Retro Techno one can feel the evolution. 

The three heroes of Detroit Techno are Juan Atkins, Kevin Saunderson and Derrick May. The last one is the most pure and the most heroic. Juan Atkins is still making music, even combining jungle rhythms True People, and Kevin Saunderson was the most popular one,who made music verging on House. Derrick May made for example The Dance. Listen to the Sample There is a basic beat (all four on the floor). There is a fast hi hat, a normal speed drum (breakbeat) and sometimes a slow anarchistic snare drum. Further, there are the strings and the rhythmic toneline, as I call it. Follow one rhythm and the others clash together as in the Renaissance polyphonic music.

Minimal Techno is just a simple rhythm and some sound. It is Techno with a small number of different noises and much empty space in the track. LISTEN LATER. From the editorial point of view, this is not an interesting genre; one sentence is enough. But musically, this is interesting, because Minimal is so basic. One could compare it with the relation between the simplicity of a string quartet against the power of a big orchestra.
Trance is one of the most popular styles at larger parties. The basic beat is 1 2 3 4, hence techno, and 140+ BPM. The hi hats between the four beats are louder than in other genres, which makes the music hotter. The bass can go higher and lower. The tracks are finished with dreamy and spacy sound scapes or the piano from Robert Miles, less furious. Very characteristic are the drum climaxes after which you put your hand in the air and jump up. It started in Germany in the beginning of the nineties - Age of LoveListen to the Sample - and grew to a world sound. ListenListen to the Sample to Protect Your Mind form DJ Sakin & Friends. Goa Trance is one degree more psychedelic, by using more trippy sounds and wibbly noises layered on each other. British band Underworld makes almost hypnotic tracks to which you can dance during their long performances. But you can listen to their albums as well. Karl Hyde experimented with vocals, just words from a diary as they came to him in everyday life. Sometimes the lyrics are almost verbatim from his notebook. Listen: Listen to the Sample to the repetition in Cowgirl from the revolutionary dubnobasswithmyheadman
Hard versions of techno are kown as Hardcore, faster versions as Gabber. Hardcore is aggressive, frenzied and occasionally abrasive, and generally sounds like chaos. The beats per minute are about 180-190 A variant is Artcore, a heavy, dark style with dark and heavy synthesizers and dark voices. It's called Gangsta as well. This is the traditional Ruffneck, listen Listen to the Sample to So Bright. From around 1998 is the Newstyle, slow hardcore (150-160 bpm) with accessible sounds and synthesizers.
About 1992, hardcore evolved in two directions: dark side and happy hardcore. Dark side evolved to Jungle. For happy hardcore the speed on the looped breakbeats was turned up, cheesy pianos were added and happy vocals. In general it sounds more cheesy.
Gabber is the hardest and fastest style. The number of beats per minute can go up to 400, but is in general about 200 bpm. Listen Listen to the Sample. The genres came up circa 1989 in Rotterdam, The Netherlands. Gabber means 'mate' in Dutch. Featuring quirky cartoonesque samples it is called happy gabber or happycore.
In England in the beginning of the nineties the Detroit Techno became popular. The Orb started to make the first chill out music, to be played after the dance, at the after party. In Sheffield the Warp label was founded. They released artificial intelligence or listening techno. It is similar to Detroit Techno due to the polyrhytmic layers, while the soundscapes were more rich. So: less dance, more listening. Listen Listen to the Sample to a track from the Black Dog Productions from 1993. The two volumes of Artificial Intelligence are classics in the genre.