Bachman Turner Overdrive
Allman Brothers
Lynyrd Skynyrd
maybe CCR but they did some blues/country like Midnight Special
Back in Black by AC/DC popped into my head instantly
Then I thought about that Back To the Future scene with Eruption by Van Halen and aliens melting his brain.
Finally, I’m reminded of the wisdom “Everybody`s talkin bout the new sound, funny but it’s still Rock & Roll to me”
Added on an acid trip flashback: Maggot Brain, Parliament/Funkadelics 
I tend to agree with that, but you then put AC/DC in the middle of the spectrum, whereas I think that they are purely “sex, drugs, and rock & roll,” and belong at that end of it.
It’s funny how that band’s sound can vary. ‘Live at Budokan’ was like polished hard rock to my ears, but I’ve seen them at a small concert hall ( theater really ) and also heard recordings/broadcasts from other small venues, and they sounded so heavy they could ‘Slayer’ a run for their money. Some of the songs, even from their earlier ( better? ) albums sound downright insipid in the studio, but harder than a cement pie in the face live. Very raw. Loved it. Still do.
Posting one of the best “old” internet sites:
Not sure how old it is, but I think I’ve known about it for at least a decade. Unfortunately, some of the linked videos are removed, but you can still dig them up on your own, outside the site.
The recently-released “Live at the Whisky 1977” illustrates this point perfectly, To quote one review, “The result: a series of fire-breathing shows that you can still hear reverberating on the Sunset Strip to this day.”
In Japan, Cheap Trick was playing to a sea of (mostly female) adolescents. At the Whiskey, they were playing to a crowd of hardcore Hollywood 18+ers.
Thank you! Where did you find that?
It’s just a common expression - even the BBC uses it, and it’s in Wikipedia.
I didn’t know (or I had forgotten) those three were called the Unholy Trinity. I just knew they always talked about three different groups as being the first heavy metal band.
Now I come to think of it, another definitely ‘hard rock’ band was Status Quo. May not have been as well known in the US, but massive in the UK at their peak.
I tend to think of the 80’s as the golden age of Hard Rock. Bands like Guns and Roses, Motley Crue, Def Leppard, Tesla, Van Halen, AC/DC, The Scorpions, Whitesnake… I’m sure I’m forgetting a bunch.
I’m one of the fans of Sixties Psychedelia who ran out and bought a Status Quo album after hearing “Pictures of Matchstick Men”. Not at all what I expected.
That sounds great. I was all psyched up to find it and buy it until I found that it’s virtually unavailable, and those that are available are super expensive. 
I think that holds true for Kiss, Motley Crue and the other bands on the HARD ROCK side. From AC/DC to the Stones gets more “radio friendly” IMHO. Eventually if you keep following the spectrum you will get into softer rock like Journey or REO Speedwagon.
Now I guess the question is where does Rush fall?
Originally, hard rock (with maybe a shading towards metal), as they were generally felt to be derivative of Led Zeppelin. But, starting with their second album, they moved increasingly into progressive rock.