The 1960's and 70's were a time of liberation, a time of rebellion against rigid rules and strict moral boundaries. In those "freedom of expression" days, an artist would typically herald their liberal attitudes as a mind-expanding trip on stage together with the audience in two ways. One was to realize audio/visually the visual and auditory hallucination as it was, and another was to play their repertoire spiritually and improvisationally under the trip. As for the latter approach, they devoted themselves solely to slow-to-mid tempo playing with low-tuned guitars in a heavy and expansive manner for playing steadily under this twilight condition. In the same time period, this approach to the musical trip was also taken on by some artists especially in the hard rock and heavy metal scene. This new style, drenched in heavy and downer psychedelia, was called "Stoner Rock". The name originates from the expression "stoned", referring to people in altered states of mind while under the influence of psychedelic substances. The Stoner Rock genre was universalized "as a strict musical style only" by the Industrial Grunge Rock genre that gained worldwide popularity in the early 1990s. The common denominator of all the artists mentioned is the representation of their personal cultural and political backgrounds, whilst playing slow-paced depressive songs with heavy guitars and echoic rumbling drums as the dominating features. Most of current outfits claiming to be the so-called Psychedelic Heavy Progressive Rock ones should be much influenced by the traditional Stoner or Grunge Rock as well as the early Psychedelic Progressive Rock. They can be considered as a borderline case between Psychedelic Progressive, Heavy Progressive, and Progressive Metal.
"Acid Folk" can be mentioned as another musical style with hallucinogenic approach. Psych Folk or Psychedelic Folk are other names for this genre, and is vaguely defined as a rock subgenre due to the mixture of folk rock and psychedelic rock. This is a style lacking in strict definitions, and it is contested whether or not the term was actually used at what is deemed the dawn of the genre. It's an undeniable fact that the Acid Folk scene gained some popularity by the efforts of artists in "The Folk Revivalism", but it's important to remember that there were two distinctly different approaches taken by those who helped shape the genre in the mid 1960's. Some folk singers approached a psychedelic rock structure as was popular at that time, while some psychedelic rock outfits tried to absorb and incorporate techniques and elements from folk rock. Both have great importance in the development of Acid Folk, and this may be the reason that strict definitions of the genre cannot be given. In view of the history, it's no exaggeration to claim that TYRANNOSAURUS REX, SYD BARRETT or THE INCREDIBLE STRING BAND in UK rock scene seasoned the "traditional" Acid Folk with a more progressive spice. They, as eccentric or heretical rock outfits, accepted and incorporated Middle-Eastern and Oriental elements or instruments, and the result was the foundation for the current progressive Acid Folk movement. And in the Eastern parts of the world, different acid streams was provided by artists such as TAJ MAHAL TRAVELLERS or MAGICAL POWER MAKO who exerted a great influence on younger progressive bands. Their amazing achievements resides in the twilight zone between the Prog Folk and Psychedelic Prog subgenres.
