 Complete the following phrase:  Soon musicians began to refer at first indirectly, and later explicitly to the drug and attempted to recreate or reflect the experience of taking LSD in their music, just as it was reflected in psychedelic art, literature and film. This trend ran in parallel in both America and Britain and as part of the interconnected folk and rock scenes. As pop music began incorporating psychedelic sounds, the genre emerged as a mainstream and commercial force. Psychedelic rock reached its peak in the last years of the decade. From 1967 to 1968, it was the prevailing sound of rock music, either in the whimsical British variant, or the harder American West Coast acid rock. In America, the 1967 Summer of Love was prefaced by the Human Be-In event and reached its peak at the Monterey Pop Festival. These trends climaxed in the 1969 