Thanks for including Beautiful Music as a factor in FM listening growth.
Too often, the story of FM among historians is all about how album rock is what made the band successful. But in reality, if you look at Arbitron numbers from the early 1970s, it is almost always a Beautiful music FM that was the first in a market to have good ratings.
The only ARB numbers I have seen from 1970-1975 are the ones printed in TV/Radio Age (just the top 5) and those in R&R. With the rare exception of a handful of rock stations like the ABC Rock N Stereo FMs or a few early FM CHRs like KSLQ or WPGC, few AOR stations had mass appeal until Lee Abrams and others fine tuned the format. Even legendary stations like KMET or KSHE were not market leaders until the late 70s.