Psychedelic trance (also known as "Psytrance" or "Goa trance") is a form of electronic dance "music" that has been parting hippies from their hard-bartered cash since the early 1990s. It combines a pattern of repetitive beats and melodies with a lot of weird noises, which supposedly lull the listener into a trance-like state. When combined with various recreational drugs, visual and aural hallucinations that appear to follow the same pattern as the music can supposedly be experienced. Generally, this results in the listeners either staring vacantly into space, or dancing like a drunk elephant wearing shoes that are too tight for their elephant feet.
It was born on the beaches of Goa, India, by expatriate hippies (such as Goa Gil), who combined the sounds of late-60s and 70s psychedelic rock with the four-on-the-floor rhythms of techno, spilling out from Detroit and Chicago.
(Further evidence that the US dropped nukes on the wrong 2 cities) Hey, Chicago was responsible for house.
The main features of psytrance are the percussion, bassline and random noises. The drums are generally made using a 16-step (i.e., 16th note) sequencer with a loud THUMP on each beat. Other little beats can be added in, but it doesn't really matter, as long as the THUMPs are there. The bassline is generally made in the same way, but consists of three or so short, staccato 16th-note 'bloops' after every THUMP. That is, 'THUMP'bloopbloopbloopTHUMPbloopbloopbloopTHUMPbloop...' This 'driving' bassline is often made with an infamous Roland synthesizer called the TB-303. When the 303 is abused, it will make strange noises. This is the basis of another genre of electronic dance music named 'Acid'.
The weird noises in psytrance, however, can be absolutely anything.
From Goa, the music spread around the world, except for America, where its arrival coincided with the Crack House Laws, which made anybody organising a gathering involving loud, repetitive music decidedly nervous. Not as nervous, however, as your average rave bunny, suddenly finding themselves surrounded by hairy, dreadlocked, pierced, tattooed hippies... and the men were even scarier.
These days, psytrance producers who aren't lying face down on a beach in Goa, can be found lying face down on the beaches of the UK, Japan, Russia, Croatia, Italy and South Africa. However, for reasons known only to them, 99% of all psychedelic trance comes from Israel. Many notable groups delight in subtle names, such as Infected Mushroom, Hallucinogen, Astral Projection and 1200 Micrograms, to name but a few.
It's also acted as a magnet for every type of New Age loony and it's impossible to move at a party without having your chakras cleansed, your crystals read, a cup of chai with all the trimmings and if you're really lucky, a pizza baked by Hare Krishnas, who offer a convert-you-while-you-wait service. Some have even cashed in on the woo-factor and there are now two Trance Institutes, studying trance (duh!). Most of the studies, however, appear to involve staring at the pretty pictures in the corner, or sitting on the floor saying, "Whee! I'm a tangerine."
 What psychedelic trance is not
Uplifting, progressive, vocal, tech trance, etc. which is generally considered awesome. They're similar in name only.
 Required listening
Although these days, psytrance appears to have branched off into two subsets - one which sounds like an angle-grinder raping a combine harvester and the other which sounds like the bastard offspring of Euro-trance ("Go on, swim into the light, fondle the dolphin, you know you want to...") there are several notable classics that anybody who wants to be "with it" (i.e. not being stared down by a mob of glassy-eyed hippes) should know. These include: (Artist name first, because some of them are weirder than the song titles)
- Cosmosis - Down at the Crossroad
- Astral Projection - Nilaya
- Transwave - Trashish
- Electric Universe - Meteor
- Hallucinogen - LSD
- Infected Mushroom - Release Me (Oh, hell with it, everything of theirs is classic apparently)
- Etnica - Starship 101
- Chi A.D. - Eye am the I
...and so on.