I have no idea. When I retire and write my book, I’ll let you know my final opinion. Certainly Ray Davies’ You Really Got Me was a hard rock song. I think ‘68 was the year though, that many rockers were consciously striving for a harder edge. McCartney of all people, put down the tracks for Helter Skelter, Birthday, Why Don’t We do it in the Road. He showed a hard edge earlier in 64 or 65 with I’m Down, which as I understand it, Martin flat refused to produce as a studio mix. Lennon did Yer Blues for the White album. Hendrix was definitely into heavy stuff. MC 5 was pretty hard. Nugent (ugh) with his Amboy Dukes stuff was certainly hard edged and had been around for some time before ‘68. There’s probably some guy out there somewhere teaching a college course called The Evolution of Hard Rock who has some thoughts on the subject. Anyway, with baseball about over, I’ll be delving into my toxic waste dump of vinyl and will see if I have a more definitive answer.