My favorite thing about Classic AT40 is hearing all the songs that have never been played on the radio since the time they were currents. I love hearing all the obscure songs and artists, especially cheesy 70s pop, for example "Popcorn" by Hot Butter which I heard on a classic AT40 from 1972.
Here's a little Las Vegas AT40 history. The show originally aired on the old KFM-102 when they were an automated Top 40 station. When KFM switched formats to AOR in the late 1970s they kept running AT40 because they didn't want KLUC to steal it away. I can remember how strange it was to hear "Funkytown" by Lipps Inc on a station that normally played bands like AC/DC and Molly Hatchet.
KLUC aired a second-tier rival countdown called "Weekly Top 30" with host Mark Elliot. Also, on Sunday nights they ran a countdown called "The Great American Radio Show" which was hosted by Michael Harrison, yes the Talkers Magazine Michael Harrison back when he was with the old KMET/Los Angeles. It was a countdown of the R&R Rock chart and many of the songs sounded totally out of place on KLUC such as Pat Travers "Boom Boom Out Go The Lights" and Ted Nugent "Wango Tango"..those were KFM songs.
The last thing KFM aired before switching to Country on 1-1-81 was the AT40 for the year 1980. In and out of the countdown they ran sweepers teasing the format flip that said they have "grown up to be cowboys".
Sure enough, just as KFM had long predicted, KLUC started running AT40 as soon as it became available. KLUC was an AT40 affiliate the very next weekend.