New audio tapes released by NASA have revealed “outer-space music” heard during transits around the far side of the moon.

The new tapes reveal audio between astronauts Eugene Cernan and John Young discussing the strange noises, which were heard during a mission in 1969. The tapes are part of a new Science Channel series, NASA’s Unexplained Files; you can watch a portion of the episode above.

“Sounds like, you know, outer-space type music,” says one of the astronauts.

The recordings were previously archived for the past several decades but are just now coming to light. A portion of the transcript, which registers at over 500 pages, can be seen below.

Some people still dispute the source of the noise, according to CNN. One NASA technician believes the whistling was a result of radio interference while others think it’s something else.

Michael Collins, who flew over the dark side of the moon during the Apollo 11 mission, reported hearing a similar “eerie woo-woo sound,” but said he had been warned by technicians beforehand that he might run into radio interference.

While it’s fun to think the noise might be some space ghost trying to spook out the astronauts, it sounds like it’s really nothing more than some radio quirk.

apollo 10 space music