As to screaming ~~ think of the Rudolf Valentino phenomenon in the mid-20s. He was admittedly a film star not a singer: but the 'screaming·at·your·idol' convention was well established when Sinatra inherited it in 1940.

What I did like about the Beatles is that, despite their name, melody took precedence with them over rhythm to a far greater extent than with many of their contemps. The baleful influence of rock, it always seems to me, is that, though there are some good tunes among all the dross [& I am merely adapting Theodore Sturgeon's indispensable Law Of Science Fiction, "90% of sf is crap because 90% of everything is crap" rather than venturing a critical judgement], it was when the beat, the riff, that constant ostinato rhythm took priority over the melody, with Presley & Haley & from then on in ~~ that was the true "day the music died".

~Michael~