One could start with the development of analog synthesizers and the music from Kraftwerk, Tangerine Dream, Klaus Schulze and Jean Michel Jarre, to which many producers of electronic dance music refer over and over, because these musicians already turned to popular electronic instrumental music and were aware of the trance effect of repetative melodic machine phrases. But that would lead too far at this point because I want to give just a brief introduction :)
The first DJ who mixed two vinyls together to produce a sound continuum for the dancers was Francis Crosso from New York in the the mid of the senventies. After house and techno music has been implemented a guy named DJ Pierre from Chicago experimented 1987 with a Roland TB 303 bass phrase synthesizer and steadily turned the frequenzy and resonance knob while playing to a drum track – acid house was borne.
This sound went from Chicago via Ibiza to Britain to usher the second summer of love and the raves on tons of exctasy pills. 1988 the KLF released „What time is love?“ and labeled this as „Pure Trance“ by themself, which could be seen as one of the first trance tracks at all. It is obvios to mention, that acid house and trance has been played in Goa, too, as well as EBM and Industrial, where DJs like this mystical Laurent, supplied the dancing crowd with this latest hype, which inspired producers to further developments and led to vinyl releases in 1991 wich already strongly reflects the Goa Trance sound of the upcoming years:
Megabeat – Twin beats, The Infinity Project – Hyperactive, Ramirez – La Musica Tremenda (already Off-Beat bass :)), Stardiver – Lifetime Mission, Komakino – Frogs In Space, Scene – The Future Of Music, The Overlords – Sundown (listen to these tracks on youtube!)
Kai Mathesdorf (mushroom magazine) proclaims „Jungle High“ (1992 Logic Records/1997 Perfecto) from Johann Bley and Ben Watkins (Juno Reactor) as the first „official“ Goa Trance track (A comprehensive History of Psytrance can be found in the online ressources of the mushroom magazine). Musicians like Bley as well as Raja Ram (The Infinity Project), who came to Goa in 1989 inhaled the spirit and went back to Britain, where they released their tracks on the specially created label from Martin „Youth“ Glover – Dragonfly. There they infected others like Simon Posford, who became a leading protagonist as Hallucinogen in the Goa music scene with tracks like „Hallucinogen – LSD„.