Recordings of the event were declassified in 2008, and will be played on Science Channel's NASA's Unexplained Files this month

They were on the far side of the moon, so it couldn't have come from Earth

Apollo astronauts who orbited the moon two months before Neil Armstrong's famous 1969 landing heard mysterious and unexplainable 'music' on its far side, out of the range of Earthly radio transmissions, it has emerged.

Recently unearthed recordings made by NASA of the journey, which took the Apollo 10 capsule around the far side of the moon, show the astronauts reacting with surprise and confusion to an unearthly howling noise in their headsets.

The sound began once the capsule was on an hour-long trip around the far side of the moon, out of the range of any Earth broadcast. At one point the baffled astronauts can be heard discussing whether they should tell NASA command or not.

Scroll down to listen to the music

Moon music: The Apollo 10 capsule (pictured) was on the far side of the moon when its occupants heard 'weird music' on the radio

Surprised: The team (pictured left to right: Eugene Cernan, Tom Stafford and John Young) debated whether to tell NASA command about the 'outer space-type music' that they heard

'You hear that? That whistling sound? Whooooooooo!' one of them says.

Another astronaut says he can: 'It sounds like, you know, outer space-type music.'

'Well, that sure is weird music,' his companion agrees.

And no, the 'music' was nothing to do with Pink Floyd's The Dark Side of the Moon, which was released four years later.

The sounds lasted almost the whole hour that the capsule was on the far side of the moon, and back on Earth the recording was shelved by NASA until 2008, when it was declassified. Now it has resurfaced in the upcoming third season of Science Channel's series, NASA's Unexplained Files.

Mysterious: Typical explanations for such sounds — including interference caused by magnetic fields or atmospheres — do not apply on the moon, leaving their origin a mystery

On the show, Apollo 15 astronaut Al Worden says: 'The Apollo 10 crew was very used to the kind of noise that they should be hearing. Logic tells me that if there was something recorded on there, then there was something there.'

The show discusses some of the possible solutions, which include a magnetic field or atmosphere interfering with the radio — but according to experts in the show, the moon has no magnetic field and not enough atmosphere to cause such issues.

The origins of the noises may, it seems, remain a mystery.