Many thanks to SRAA Contributor, Brian D. Smith (W9IND), who notes:

Want to know what shortwave radio sounded like in 1974? This 55-minute recording, recovered from a cassette, was never intended to be anything but "audio notes": I was an 18-year-old shortwave listener who collected QSL cards from international stations, and I was tired of using a pen and a notepad to copy down details of the broadcasts. I wanted an easier way to record what I heard, and my cassette tape recorder seemed like the perfect means to accomplish that goal. But it wasn't. I soon discovered that it was simpler to just edit my notes as I was jotting them down — not spend time on endless searches for specific information located all over the tape. To make a long story shorter, I abandoned my "audio notes" plan after a single shortwave recording: This one.  Still, for those who want to experience the feel of sitting at a shortwave radio in the mid-1970s and slowly spinning the dial, this tape delivers. Nothing great in terms of sound quality; I was using a Hallicrafters S-108 that was outdated even at the time. And my recording "technique" involved placing the cassette microphone next to the radio speaker.Thus, what you'll hear is a grab bag of randomness: Major shortwave broadcasting stations from Canada, Argentina, Spain, Germany and Albania; maritime CW and other utility stations; and even a one-sided conversation involving a mobile phone, apparently located at sea. There are lengthy (even boring) programs, theme songs and interval signals, and brief IDs, one in Morse code from an Italian Navy station and another from a Department of Energy station used to track shipments of nuclear materials. And I can't even identify the station behind every recording, including several Spanish broadcasts (I don't speak the language) and an interview in English with a UFO book author. The following is a guide, with approximate Windows Media Player starting times, of the signals on this recording. (Incidentally, the CBC recording was from July 11, 1974 — a date I deduced by researching the Major League Baseball scores of the previous day.)GUIDE TO THE RECORDING0:00 — CBC (Radio Canada) Northern and Armed Forces Service: News and sports. 
7:51 — RAE (Radio Argentina): Sign-off with closing theme
9:14 — Department of Energy station in Belton, Missouri: "This is KRF-265 clear."
9:17  — Interval signal: Radio Spain.
9:40 —  New York Radio, WSY-70 (aviation weather broadcast)
10:22 — Unidentified station (Spanish?): Music.
10:51— Unidentified station (English): Historic drama with mention of Vice President John Adams, plus bell-heavy closing theme.
14:12 — RAI (Italy), male announcer, poor signal strength.
14:20 — Unidentified station (Spanish): Theme music and apparent ID, good signal strength.
15:16 — Unidentified station (foreign-speaking, possibly Spanish): Song, "Chirpy Chirpy Cheep Cheep."  
17:00 — Deutsche Welle (The Voice of West Germany): Announcement of frequencies, theme song. 
17:39 — Unidentified station (English): Interview with the Rev. Barry Downing, author of “The Bible and Flying Saucers.” 
24:36 — One side of mobile telephone conversation in SSB, possibly from maritime location.
30:37 — Radio Tirana (Albania): Lengthy economic and geopolitical talk (female announcer); bad audio. Theme and ID at 36:23, sign-off at 55:03.
55:11 — Italian Navy, Rome: “VVV IDR3 (and long tone)” in Morse code.