Même si un peu loin du texte d'origine

English term (edited): a freak out, a turn-on and a tune-in

Monterey [Pop festival Monterey] still represents the finest flowering of the hippie dream, a freak out, a turn-on and a tune-in that performer Art Garfunkel described as "the cherry on top of the sundae that was the '60s. It was totally unprecedented and the audience was totally unprecedented in their joy."

"... une occasion pour se libérer, activer ses sens et être en harmonie ...

It's a reference to the famous counterculture phrase popularized by Timothy Leary (=> "hippie dream"):

"Turn on, tune in, drop out"

"Leary later explained in his 1983 autobiography Flashbacks:

"Turn on" meant go within to activate your neural and genetic equipment. Become sensitive to the many and various levels of consciousness and the specific triggers that engage them. Drugs were one way to accomplish this end. "Tune in" meant interact harmoniously with the world around you - externalize, materialize, express your new internal perspectives. "Drop Out" suggested an active, selective, graceful process of detachment from involuntary or unconscious commitments. "Drop Out" meant self-reliance, a discovery of one's singularity, a commitment to mobility, choice, and change.
Unhappily my explanations of this sequence of personal development were often misinterpreted to mean "Get stoned and abandon all constructive activity"."
[http://en.wikipedia.org/wiki/Turn_on,_tune_in,_drop_out]

same as "flowering" wasn't used by accident:
"flower generation
A term referring to the people in the 60's-70's known as Hippies. Talking about their entire generation.
John Lennon was from the Flower Generation."
[http://www.urbandictionary.com/define.php?term=flower genera...]
Also:
[en.wikipedia.org/wiki/Hippie]
[http://en.wikipedia.org/wiki/Flower_power]
[http://en.wikipedia.org/wiki/Flower_child]

ou bien "élargir sa conscience et partager dans l'harmonie"
ou bien "éveiller son âme et suivre la voie de son coeur".

Car c'est l'idée si l'on part du principe qu'il s'agit du "turn on, tune in, drop out" de Leary.

Son explication : "Leary later explained in his 1983 autobiography Flashbacks:

"Turn on" meant go within to activate your neural and genetic equipment. Become sensitive to the many and various levels of consciousness and the specific triggers that engage them. Drugs were one way to accomplish this end. "Tune in" meant interact harmoniously with the world around you - externalize, materialize, express your new internal perspectives. "Drop out" suggested an active, selective, graceful process of detachment from involuntary or unconscious commitments. "Drop Out" meant self-reliance, a discovery of one's singularity, a commitment to mobility, choice, and change. Unhappily my explanations of this sequence of personal development were often misinterpreted to mean "Get stoned and abandon all constructive activity".[4]"
http://en.wikipedia.org/wiki/Turn_on,_tune_in,_drop_out

pour turn-on : quête de spiritualité, exaltation / elévation spirituelle, recherche de la vérité

D'autres traductions qui ne reflètent pas l'idée de Leary :

"« Turn on, tune in, drop out »/ “Viens, mets-toi dans le coup, décroche”

plutôt : allume, branche-toi, laisse aller. N’est-il pas, alec ?"
http://passouline.blog.lemonde.fr/2011/07/06/les-archives-pl...

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Note added at 1 hr (2013-08-22 10:53:44 GMT)
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On pourrait peut-être rester plus façon 21e siècle avec
"Exaltation et partage en harmonie", non ?

comme il s'agit des premiers 'happening' ça pourrait marcher?