This review by Frank Ahrens in Nov. of 2001 for Washington Monthly of the book by Richard Neer "FM: The Rise and Fall of Rock Radio" gives some insight into the rise and fall of (the Music of) Rock Radio.Here's a snippet from the review:The sad truth about modern radio is that it's not--repeat not--about playing music or talk that listeners like to hear. Radio is about promising discrete audiences to advertisers--it's an advertising-delivery vehicle. The truth is that most radio listeners don't want to hear songs they don't recognize or that haven't been sufficiently hyped. Only what researchers call "sophisticated" listeners are into music experimentation--and they don't comprise a big enough demographic to merit many radio stations of their own.http://www.findarticles.com/p/articles/mi_m1316/is_11_33/ai_80533149/pg_1