In my view, Drugs were used as a conscienceness expander. The new view on things gave new insight to how people saw the world.
Beatles is a great example, but there is plenty of their music that was good before Sgt. Peppers and Magical Mystery tour.
Pink Floyd for example, people think of "The Wall" and "Darkside of the Moon", that was only the climax of their carreer. When the band first started out, they fooled around with the synthensyzer and what not, after they hit underground, the idea of the use of drugs became more present, Syd Barrett started taking them after they started to get known more, which eventually led to his mental unstableness. But thier stuff like "Meddle" and " Piper at the Gates of Dawn" is amazing, with or without the use of drugs. As the years went on, the world started to shift around, along with all the music out there. "Atom Heart Mother" came out, It was a different, yet similar sound. Thier music changed as the world did, just like all the bands. Roger Waters started writing more about the WWII years ("The Wall" and " The Final Cut")
Waters left, throwing out the band, they resurfaced in a new era, the dreaded 80's. Music had changed again.
But not all music that time was drug influenced. Supertramp, for example was a totally different sound.
My point is, drugs in just a small contribution to how music is.
Hope you like my history of Pink Floyd.
I also hate things.
"Reminds me of you NS faggots. " - glass
I ski Kicking Horse, pm me if you come this way