Math prof Jason Brown thinks he has it all figured out at http://www.abc.net.au/news/science/2017-11-05/a-hard-days-night-how-mathematics-revealed-beatles-secret/9093348

Math prof Kevin Houston thinks Brown has it all wrong at http://www.kevinhouston.net/blog/2014/12/the-beatles-magical-mystery-chord-2/

Musician going by the handle Waynus of Uranus writes essay Houston relies on at https://sites.google.com/site/ahdnchord/home

Bottom line: it helps to know some math, or at least to have some software that knows the math, but it also helps to know something about what the engineers do to the music between the time the instruments get played and the time the record gets pressed.