Special things were happening in the late 1960s with the development of drug inspired psychedelic music in San Francisco and London.
The Beatles popularised it with songs like Strawberry Fields Forever, Lucy In The Sky With Diamonds and I Am The Walrus.
Other groups like the Grateful Dead, Jefferson Airplane and The Doors were taking it much further. Sometimes to happy, relaxing places and sometimes to the darker, scarier side.
What Are the Best Psychedelic Live Albums?

You can see the complete list of readers polls at Live Album Polls.
Of the Iron Butterfly Live Albums in My Opinion Live in Copenhagen 1971 is by Far Their Best