Weird space music heard by Apollo 10 astronauts on the far side of the moon. Or at least that's what it seemed like. So of course the story was quickly followed by a bunch of Pink Floyd jokes, puns and references. And of course the conspiracy theorists had to talk about how weird it was these transcripts were kept classified until 2008, but then again so were all of Apollo 10's transcripts. You can hear the audio here.

Basically what the astronauts are hearing though, is something called Heterodyning. It's a process where two frequencies are mixed or combined to create completely new frequencies. This is actually what a theremin does. And it's not surprising the astronauts thought it sounded "like an outer-space-type thing". I've seen someone perform the theremin live, and it's a trip.

It's not unheard of for popular artists to use the theremin. Led Zeppelin, The Rolling Stones, The Beach Boys, Rush, and yes even Pink Floyd have used the theremin. But it was in the song Echoes from the album Meddle. As far as I can tell, they didn't use a theremin on the Dark Side of the Moon.

The most likely cause of the eerie sounds caused by Heterodyning? Interference between two radios that were too close to each other in the lunar module and the command module.