AM radios were easy to understand. The strength of the signal goes up and down, and the audio follows. FM radio is a little more difficult. [AllAmericanFiveRadio] has an old tube FM set and takes us on a tour of how the FM discriminator works. You can see the video below.
This is a companion discussion topic for the original entry at https://hackaday.com/2024/01/21/fm-radio-is-discriminating/