I've always viewed psychedelia, if it's to be taken as a single entity, as a broad church governed by the light, and by the light only, into which darkness comes. I see punk in similar terms, as an open forum for the expression of individualism and creativity. Its rapid inflections can be seen across the artistic spectrum, be it painting, sculpture, comedy, philosophy, fashion, photography, poetry, literature, or the often hyperactive medium of dance. Its branches reach deep inside science, all the while violating, be it medicine, psychology or psychiatry.
It's connected to the counterculture movement for many people, despite its ancient origins, as these things are inextricably linked by historical document. Political activists attemped to use psychedelic art as a tool to transmit subliminal messaging, countering narratives built through government usage and government-sponsored corporate control of the commercial airwaves. Journalists, diarists and writers diligently examined both stark immersions and peripheral viewpoints associated with the ravages of drug culture. People also took time to study its transcendental aspects.
In film, the counterculture movement was linked to the rise of the independents, some of whom targeted flaccid fleapits, decaying grindhouses and dilapidated drive-ins as being suitable locations to screen subversive works of limited commerciality. Some underground filmmakers would eventually be hired by the same major studios that had suppressed them, helping reshape the culture from within, while others would continue to work on the fringes of polite society due to the greater artistic freedoms on offer.
As the 1960s progressed, it had become clear that avant-garde music had opened new doors. Jazz was becoming increasingly more experimental, folk was branching way out and classical composers were constantly reaching for new ideas. Some theorise that psychedelia created a bridge between garage rock and punk rock, movements marked by a sense of gay abandon; sibling subgenres infused with similarly creative ideas, base components and a revolutionary spirit, leading to some degree of crossover. There are those that argue the psychedelic movement birthed avant-folk and her kissin' country cousins, experimental funk and the p-train, heavy metal and progressive rock, alternative musical subgenres characterised by risk and innovation.
As I understand things, business executives and sales operatives actively sought to pigeon-hole the arts for commercial purposes, which would, of course, be perfectly understandable. But for said critics seeking to compartmentalise the arts for reaons of simplification, anayltics, or hierarchy, it's perhaps worth noting that there are musical groups widely acknowledged as having delved into psychedelics who were said to be divided themselves; this could cause units to fracture, bands to splinter, collectives to be ripped apart under the weight of intense pressure. I guess, sometimes, group members inevitably found themselves pulling in different directions, as can be the volatile nature of such things.