Throughout the modern pop and rock era, the world of music publishing has undergone numerous changes (from the 1950s to the present). The most significant change has most likely been the gradual shift toward putting power (and most of the money) in the hands of songwriters rather than publishing companies, which used to wield the most power and control.
Back in the 1950s, rock and R&B artists would sell their entire copyrights to their labels for around $250 per song. For this sum of money, they would assign not only their publishing share but also their entire writer's share! One of the major companies I worked for owned the classic hit songs of a big-name '50s star and would lawfully keep 100 percent of the royalties, without having to pay any royalties to the hit writer.
In the 1960s, at the very least, songwriters kept their songwriter's share, splitting royalties equally with the publisher. Because the mechanical royalty rate (for records sold) was only two cents per unit sold, calculating the earnings was simple: one penny for the songwriter and one penny for the publisher.
