I asked Alexa to play The Mamas & The Papas the other night, and I wondered why they were ever categorised as "folk-rock." Their music was neither. The covered some R&B songs and sorta-rock, but they gentled-down lots of it, as in "Twist and Shout," and "Dancing' In The Street." Cass sang some 1930s and 40s numbers in what was much more of a jazz than folk expression - "Dream a Little Dream of Me," for example.
They looked like folkies, and they played guitars. They had started in Greenwich Village and knew the folk scene and were known by them. The first hit "California Dreaming" had a different tone, more depressed than wistful and poignant in it's first iteration, but they were actually in California by the time it was recorded and Lou Adler and PF Sloane sweetened it up. Harmony singing was very big with the popular folk musicians, such as Kingston Trio or Peter, Paul, and Mary, but harmony was big with everyone in those days: "Ruby Tuesday," "You Keep Me Hangin' On" (either version), and "See You in September" were not considered folk classics, after all.
My wife and I used to force the children to listen to us singing "Creeque Alley" in the car, mostly because it was an accomplishment to keep the lyrics and harmony straight and lots of fun. (Also, I was a Spoonful fan.) I should have picked up the intended change right from the first line. "John and Michi, were gettin' kind of itchy, just to leave the folk music behind." Hiding in plain sight.
They were about as dysfunctional as you can imagine, Michelle with affairs and flings, John with heroin addiction, Denny alcoholism, and Cass with arrests for minor theft and storming out of rehearsals and get-togethers with some frequency. When people had sweet gentle harmonies, I tended to think of them as sweet, gentle people. Not a reliable rule of thumb.
There is this from "The Sketch Show."