I first heard this over twenty years ago. Just a hauntingly beautiful sound.
Holger, better known for the experimental music group, "Can", was listening to crackly channels on a short wave radio. He heard this song on Radio Tehran, in 1979, taped it, and then set to creating the music, splicing and editing the voices...
But rather than me write the story, I'd recommend you read this piece from Alan Warner in Granta.