In Technology Review, author and essayist Chuck Klosterman delivers a short introduction to the stars of space rock, from Pink Floyd (above) to Hawkwind to Spacemen 3:
Space is a vacuum: the only song capturing the verbatim resonance of space is John Cage's perfectly silent "4'33"." Any artist purporting to embody the acoustics of the cosmos is projecting a myth. That myth, however, is collective and widely understood. Space has no sound, but certain sounds are "spacey." Part of this is due to "Space Oddity"; another part comes from cinema, particularly the soundtrack to 2001 (the epic power of classical music by Richard Strauss and György Ligeti). Still another factor is the consistent application of specific instruments, like the ondes martenot (a keyboard that vaguely simulates a human voice, used most famously in the theme to the TV show Star Trek). The shared assumptions about what makes music extraterrestrial are now so accepted that we tend to ignore how strange it is that we all agree on something impossible.
The application of these clichés is most readily seen in the dawn of heavy metal. The 1970 Black Sabbath song "Planet Caravan" processed Ozzy Osbourne's vocals through a Hammond organ to create a sprawling sense of ethereal distance. Deep Purple's 1972 "Space Truckin'" used ring modulation to simulate a colossal spacecraft traveling at high speed. The lyrical content of Led Zeppelin's "No Quarter" is built on Norse mythology, but the dreamlike drone of John Paul Jones's mellotron and Jimmy Page's ultra-compressed guitar mirrored the sensation of exploring an alien landscape. Unsurprisingly, the ambiance of these tracks merged with psychedelic tendencies. The idea of "music about space" became shorthand for "music about drugs," and sometimes for "music to play when you are taking drugs and thinking about space."