Psychedelic rock is a first came around in the late 1950s. It was used as a way to break free from musical rules and develop new techniques. It was about breaking the boundries and artists often took powerful drugs to see past reality which often led to early death. Things like the whammy bar, the wah-wah pedal and amplifier distortion were dicovered. Songs were going way past the under 4 minutes rule of the radio and really twisting and experimenting with music. Famous psychedelic rock artists are Jimi Hendrix, The Beatles and Pink Floyd.