The first prototype, which had all of the main features that we think of as being integral to the "Compact Disc", was made in 1977, I think. There were earlier attempts with analog audio on optical media in 1974, but there was too much noise. LaserDisc "DiscoVision" was from this era, too.

Oh wow. I thought LaserDiscs were way later too. I guess it takes a while to develop something from a technology to a consumer product. And also I was a kid in the 80s so I wasn't paying that close attention to when these things were coming out

LaserDiscs are just a raw analog 10MHz NTSC/PAL FM signal etched into the polycarbonate (It's pulse-width modulated if I remember correctly.) For Audio Compact Discs (Compact relative to LaserDisc) 10MHz is overkill for human hearing, so they PCM encoded the audio to get a ridiculous 110db S:N ratio