(Pictured: Charlie Daniels in the 70s.)

Forty, as in Top 40, is an arbitrary number. It goes back to the days when a radio format was first devised that would repeat the most popular songs of the moment over and over. If I’m recalling correctly, 40 represented the number of songs a radio station could play in approximately three hours before starting to play them again.

There are people in radio and out of it who will tell you that as a practical matter, only 10 or 15 songs are truly “popular” at any given moment. And even a song that rides high on the chart might not be all that popular with the audience. Radio people have talked for years about “turntable hits,” records that get airplay without inspiring people to buy them. (This phenomenon still exists in country music today, where a song can top the airplay chart while barely scraping the lower reaches of the sales chart.) So in any given week, the Top 40 contains songs that are popular, songs that were popular but aren’t so much anymore, songs that may become popular eventually—and maybe even songs that are never especially popular at all.

We saw this phenomenon the last time we looked at an American Top 40 show from 1973, and that long list of songs that were on the show but not charted at WLS in Chicago, one of the country’s leading Top 40 stations. We could make a similar list from the show dated August 25, 1973: “Future Shock” by Curtis Mayfield, “There It Is” by Tyrone Davis, “Nobody Loves You When You’re Down and Out” by Bobby Womack, “I Was Checkin’ Out, She Was Checkin’ In” by Don Covay, and “Why Me” by Kris Kristofferson. These songs were popular in some places and on some formats—all except for Kristofferson were significant R&B chart hits—but they weren’t broad-based pop hits and they didn’t stick around long (again, with an exception for Kristofferson).

I would have guessed that several other songs found on this week’s Top 40 never charted on WLS, like “Cleopatra Jones” by Joe Simon, “The Hurt” by Cat Stevens, or “Believe in Humanity” by Carole King, but they did—and in the case of Stevens and King, for nine and seven weeks respectively. I don’t remember hearing them, though. Whether I remember hearing a song is probably not the best metric, however: “I Believe in You, You Believe in Me” by Johnnie Taylor charted 10 weeks and made #10 on the WLS chart, and I don’t remember hearing that one, either.

Another thing that struck me listening to this show was the relative lack of movement. True, the debut songs come zooming in as usual (all except “Future Shock,” which crept from #41 to #40 (and would go to #39 on September 1 and then out of the 40) and several declining songs fall the customary eight or 10 or a dozen places. But among the 40 there are seven songs in the same positions as the previous week; “Live and Let Die” by Wings (#2) and Charlie Daniels’ “Uneasy Rider” (#9) are in their third week at the same spots. Five songs move one place (two up, three down), and seven songs move two places (four up, three down). It would take somebody with better data analysis skills than I have—and a better work ethic—to tell how that compares to a typical week, but it seems a little slow to me. “Behind Closed Doors” by Charlie Rich holds at #36 on its way out of the 40, which seems weird, but not as weird as what Bloodstone’s “Natural High” had done. The record had peaked at #10 on July 21, then fell to #15 and then to #23, where it stayed for three straight weeks before sliding to #37 in this week.

But back to the idea of relative popularity: songs that are popular for a moment don’t necessarily endure through time. Certain songs on this chart certainly have: “Feelin’ Stronger Every Day,” “Here I Am (Come and Take Me),” “We’re an American Band,” “Saturday Night’s Alright for Fighting,” “Smoke on the Water,” “Diamond Girl,” and “My Maria” seem like all-timers to me, although your mileage may vary. But other high-riding hits seem out of time now. “The Morning After” was a #1 hit, but if it got much radio play after it left current rotations, it was because a running time of a little over two minutes made it useful for timing up to the network news at the top of the hour. And  though “Delta Dawn” also hit #1, when the last time you heard it on the radio?