Radios became popular in the 1920's, almost a century ago. From Cole Porter to Woody Guthrie, from Metallica to Kendrick Lamar, there have been many styles, fads, and phases of music since. But something different happened from the mid 60's through very early 70's. Songs like "Gimme Shelter, "Visions of Johanna", or "Bridge Over Troubled Water" -- or albums like Abbey Road, or Tommy, or Highway 61 Revisited -- probably could not have come out at any other time. And, certainly could not have come out all on top of each other at any other time with scores of other works also deserving of mention.