[Hemingway's Ghost]

But they did not anymore greatly expand the horizons of music.

No, they just pioneered about a thousand studio techniques and introduced a bunch of non-traditional instruments (sitar) and arrangements into popular music, that's all. Before "I Feel Fine," feedback even rarely made its way into finished products.

Ever hear the tune "Tommorrow Never Knows"? That came out in '66, and it still sounds current.

[CyberCowboy777]

I think you meant to say "Before "I Feel Fine," feedback even rarely made its way into finished products of popular music."

I did say they were accessible.

The era certainly did pioneer studio/production work (see Beach Boys, Pink Floyd, ect.) and the Beatles were apart of that.