So the commonality between psychedelic anything in music is: sound effects.
Trance has no sound effects
Psy trance has sound effects
Rock has no sound effects
Psychedelic rock bands used to approach early sound effect producers and pay them to get one sound effect to add to their song, it would make it psychedelic.
Many of these sound effects are within us to begin with, many people have heard the 'psychedelic' sound effects on psychedelics, and then reported how reminiscent the sound is when they hear it in music later on.
Its the sounds of how we interpret sound, its the speech before speech, its the speech before sounds, its why words and sounds mean what they do, its the impact of sound on our natural understanding as living creatures. Its psy.
It reared its head in the 60's first with psychedelic music, people were engaging in the work of expanding the conscious experience of sound, and using psychedelics to explore the mental impact of sound in heightened states, first the 'fuzztones' were found, later on distortion oriented rock which leads to all forms of modern rock and metal. Other branches expanded the 'psy' element, the psychedelic experience of sound effects on our minds.
This was the root from where all our modern music has branched, the setters of these trends were the first users of the synthesizer, the samplers later on and the early sequencing possibilites. These were the early minds into the alien language we today call 'psy'.
The modern evolution of psy is music that has a type of beatbox like conversation with itself. Its also a way of life, of remanufacturing sound again and again to achieve its higher forms.
Good psytrance has lots of sound effects, modern psytrance raises the mastering bar every year, good new psytrance has all sorts of sound effects mastered in a way that the sounds end up having a 'conversation', or phrasing, with call and response usually being a key element to holding it all together.
This is the exact same factors that makes tribal dance music in ancient times. The sounds, the conversations, the phrasing with call and response, on top of rhythms that roll on and on with micro-timing variations.
It is the essence of our origins, it is our root psychology, it is the archaic revival calling for man to connect with the earth through dance. The psy has been calling in our conscious minds since the psychedelic festivals of the 60's, the first echo of the natural self, and the time is here for us to connect once again and learn the ancient languages of our own consciousness.