cannibis i dont think has anything to do with the "speed" of music. as stated above 20s, 30s, 40s, and even today jazz musicians smoke pot.in the 60s other drugs stared coming into the seen like lsd and cocaine. cannibis may have something to do with the intensity of the music, but speed and intensty are two differant things. for instance check out some of the hippie bands that are still popular today like the dead (ok so im a dead head and im partial to them) but they are not that fast but way intense. now for bands today like wide spread panic, gov't mule, sting cheese incident, or ekoostik hookah. same thing not fast and hard but very intense.

and as far as three basic chords alot of todays music stil uses them same three basic chords, soe have expaned to four