A story has recently swept the internet about "strange space music" heard by the crew of Apollo 10 when they were looping the moon in 1969. The source of this meme was a Science Channel show called "NASA's Unexplained Files," in which a typically poor piece of research was used to create a hook in the show. Such phrases as "recently declassified" and "mysterious music," and of course the de-rigueur startled sounding quotes from the Apollo astronauts on that flight all added fuel to the fire.
Too bad it was just radio interference.
To the point, here's a quote from Gene Cernan, the Lunar Module Pilot on Apollo 10, talking to his commander Tom Stafford on the intercom:
"It sounds like, you know, outer space-type music."
"You hear that? That whistling sound? Whooooooooo!"
"Well, that sure is weird music!"
"It's unbelievable! You know?"
"Shall we tell them about it?"
"I don't know. We ought to think about it."
That last line may have been the clincher for the conspiracy buffs. But the truth, as usual, is much more sedate.
The Apollo spacecraft used many radio frequencies to communicate voice signals from itself to the ground, from the Command Module ("capsule") to the Lunar Module, and to send non-verbal engineering data to Earth, etc. Add to this the radio beacon each craft carried, multiple radar signals, thousands of potentially "leaky" electronics on each craft, and more, and you have a literal hash of radio and other EM radiation all over the place during those flights. This was 1960s technology, which required more power and leaked more electromagnetic energy than today's radio technology. The result? Weird radio sounds.
As any radio tech will tell you, when you have multiple signals operating in proximity, if a couple of them are close in frequency, you also get interference--sometimes very bizarre sounds. Like, for instance, "Woowoo!", as described by the crews of Apollo 10 and Apollo 11.
As for NASA "recently declassifying" this material... no. I read these flight transcripts in the 1990's in the national archives, as did thousands of others. Many of us also heard the audio tapes from the flights. What was recently changed was that NASA added these bits to its website, and that's what apparently got the Science Channel team worked up.
Oops. Should have checked some older references guys, like any one of a few dozen books about the Apollo program. Or, next time, just ask a space author. There's a number of us, and we often have time on our hands.
For more on this non-story, head over to this well-done piece in HuffPo: http://huff.to/1XE8WHT.