Soft rock as a genre distinction has come to refer specifically to a style of rock that emerged in the early 70s, both as a reaction against the increasingly heavy music that dominated rock at the time, and also as a reflection of the changing priorities of the Baby Boom in the early 70s. What set 70s soft rock apart from its 60s' counterpart, which for lack of a better word is usually just called "pop", is that in the 60s pop existed for those who simply didn't like rock; the 60s' pop artists usually were vocalists who were stylistic throwbacks to the pre-rock era. Soft rock developed organically to suit the needs of those who did have rock listening experience; as such, it can be considered a bona fide rock genre.
Soft rock became hugely popular later in that decade. By 1977, some radio stations, like New York's WTFM and WYNY, had switched to an all-soft-rock format. [1] Around that same time, Chicago, which had previously been a jazz-rock band, switched to soft rock and reached their biggest commercial successes. Even Led Zeppelin, considered by some to be standard bearers of hard rock, flirted with the genre at the time in songs like 1979's "All My Love". By the 1980s, tastes had changed and radio formats reflected this change; the genre evolved into what became called "adult contemporary", a pop categorization that bore less overt rock influence than its forebear.