I've always been fascinated with the creative artwork and stunning visual effect of concert posters from the late 1960s. Psychedelic drugs, revolutionary ideas and new ways of thinking were everywhere - through the emerging pop culture and the up-and-coming music scene of the era. 
This had a strong influence on the design aesthetic. The vibrant contrasting tones with vivid stripe effects, bold colors and weird, wild & wonky fonts. It stemmed from 
op art influences which were a hot & popular trend in the mid 1960s. This artwork not only helped to promote and advertise performers of the day but also reflected their music.
Here's a small but 
smokin' sampling of music concert posters from that time - mainly from the American West Coast.
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"Bill Graham Presents The Fillmore" Concert Poster by Bonnie Maclean, October, 1967. 
 
 
 
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| "Bill Graham Presents The Fillmore" Concert Poster by Bonnie Maclean, July, 1967. |  
 
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"Big Brother & The Holding Company" Concert Poster by Joe Gomez 
Avalon Ballroom, San Francisco, November, 1967. | 
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| Dance Concert Poster by Bob Schnepf, Avalon Ballroom, San Francisco, December, 1967. | 
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| The "Jimi Hendrix Experience" Poster, Fillmore East, San Francisco, 10th May, 1968. | 
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"Moby Grape and Big Brother & The Holding Company" Concert Poster,  
The Ark, Sausalito, CA, 4th November, 1967. | 
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| "The Who" Concert Poster by Rick Griffin, Hollywood Palladium, 13th June, 1969. | 
These last two aren't psychedelic concert posters but magazine covers which paid homage to the fashionable trend of the times.
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| Playboy Magazine Cover, December, 1967. | 
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| Lui Magazine Cover #49, France, January, 1968. |