I worked as a Top 40 jock in the mid-70s, but it was in a small market where (at least during my shifts) there were very few commercials. So we could, and did, play longer songs. And every jock knew to put on Stairway to Heaven or some other 7-minute album cut when nature called.
As noted, the record companies would send us special versions of lots of songs, and seldom were they more than 4:00. There was no rule in writing, but the received wisdom was that anything over 3:30 was harder to get added to the playlist at the powerhouse big-city rockers like WABC, KHJ, WLS, etc.
There actually was a promo edit of “American Pie”, although from what I understand few stations actually played it. “Stairway” never got released as a single in the 70s, but quite a few top 40s actually played it in full. Led Zeppelin’s record company definately wanted to release a 45, but since the band refused to authorize an edit they couldn’t.
Going back to the original question, you’d see occasional long singles get top 40 airplay (such as the well over four minute “El Paso” which was the first no.1 single of the sixties). But those were typically huge hits; “Piano Man” has been ubiqutous so long we forget it didn’t even make the top 20 in its first release. Had it been a big hit, undoubtedly top 40 stations of the day would have played it in full.
The song from “Led Zeppelin IV” that you heard back on AM radio back in the day was “Black Dog”. I can’t remember if it there was a single edit. “Stairway to Heaven” was more of an FM radio song.
Kunilou’s description of teenagers of the time has my older sister down to a T. She drove with her left hand on the steering wheel and her right hand firmly planted on the push buttons of the AM radio ready to change stations as soon as a commercial or a song she didn’t like came on. Another thing, at least as far as my family goes: no tape decks. Hell, it was a big enough deal to convince Dad to get a car with an AM radio. I don’t think the FM band on radios became commonplace until the mid 1970s.
The keyboard solo is just plain awful - discordant and boring. The guitar is adequate, but no one is going to confuse it with “great” and considering you have to endure the horrible organ solo to get to it, the single version is infinitely better.
The pre-war 78rpm singles were typically maxed out at 4 minutes, but 3 minutes was the generally preferred maximum.
45s “mimicked” 78s to some extent. You could get 5 minutes on them (more if you gave up quality for 45 EPs, for example).
Thru the 50s and early 60s, the DJs and station managers really preferred songs that were 2:30 and under. A lot of the classic hits in that era were as short as 2 minutes. 3:05 was considered a quite lengthy song for radio.
(I wonder if the rule was actually 3:00 not counting DJs talking over the beginning and end of the song.)
One song that helped break the barrier was 1966’s Good Vibrations: 3:35. Played it’s entirety, hitting #1 and selling over a million copies. But AM still remained somewhat conservative on record length while FM moved on.
I had just started high school when “Who Are You” was released (and Keith Moon died shortly afterwards) and we would gather around the radio whenever that song came on and act like we’d never heard That Word before.
