Mr. Pop History – When you study the history of AM, FM, and various music formats over the years, the traditional top-40 format of playing the hits, sticks out. Some stations played more than 40, others less, but KFRC-FM (K-106) in San Francisco, played with a continuous top-20 countdown format. That’s right – more than several times a day, the station, mostly automated, counted down the top-20 hits, throwing in some new releases. Interesting, to say the least. This was during the mid-1970′s, when some FM stations would try anything.