Actually... could you link up some earlier Doom stuff? Or give me a pointer?
I'm not a massive Beatles fan, but every now and again I'll notice something they did and realise (again) they some good songs. My 8 year old is into them, so now I'm listening more.
And I'm obviously not all that well versed in Doom either. That track, that sort of howling wind type noise, that sounded like Burzum, and the chord progressions sounded like metal. I was always told that Black Sabbath would have been the first lads making metal though. I can't listen to that Beatles track and not hear fully formed Metal.
I'm trying to think. Cromagnon were around in the late 60s too. But they weren't as Doomy sounding, I think?
Early lo fi blues, yeah. I can see that now that you mention it. I didn't associate that before.
edit - @moose mentioned Blue Cheer. I'm listening now.
The Groundhogs, Randy Holden (Population II), Sir Lord Baltimore, Pentagram off the top of my head. They're usually referred to as proto metal or proto doom.