New, declassified audio that caught the moment astronauts on the Apollo 10 heard “outer spacey” music as they passed behind the dark side of the moon was released by NASA recently.

The is the newest focus of the Science Channel’s "NASA’s Unexplained Files."

During the uncovered audio, you can hear astronauts Thomas P. Stafford, John W. Young and Eugene A. Cernan discuss the strange music as they made the hour-long trip around the moon.

“The music even sounds outer-spacey, doesn't it?” asks one of the astronauts on board. "You hear that? That whistling sound? Wooooo?"

Left to right; Eugene Cernan, Thomas Stafford and John Young in spacesuits in front of a representation of the lunar surface.

(SSPL/Getty Images)

"Sounds like … you know, outer-space type music," another man replies.

While traveling behind the moon, all communication is lost between the Apollo crew and NASA, so anything said or heard is unattainable until the astronauts do a data dump once they emerge from the moon’s shadow.

The crew onboard discusses the strange noises multiple times, even questioning whether they should inform NASA about what they heard.

“That’s just like something from outer space, really. Who’s going to believe it?” one crew member asks.

“Nobody. Shall we tell them about it?” is heard in reply.

After the mission was over and the crew had safely landed in the Pacific Ocean, NASA deemed the recordings as “classified” and locked away the data in their archives for decades.

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“NASA would withhold information from the public if they thought it was in the public's best interests,” Al Worden, a Command Module Pilot on the Apollo 15 mission, said during the episode.

NASA scientists believed the sounds the crew was hearing was caused by interference from spacecraft radios. This kind of event has been seen with magnetic fields or atmospheric interference, however , says Space.com.

Similar sounds were picked up by the Cassini spacecraft from Saturn, though those noises came from the , says Independent.

Morden, however, doesn’t buy the radio interference explanation.

“The Apollo 10 crew is very used to the kind of noise that they should be hearing,” said Worden. “Logic tells me that if there was something recorded on there, then there was something there.”

The crew of the Apollo 10 mission never publicly discussed the incident.

MORE ON WEATHER.COM:NASA's Project Apollo Archive