Before tape recorders made it easy (enough) to save a copy of your favorite song, clever music fans turned to records to duplicate music for their own use and help it spread. According to NPR, this was a particularly important tool for residents of the Soviet Union who, during the 1950s and earlier, used it for gaining access to banned music, particularly from the West. At the time, vinyl was scarce, however, so they ended up using a different material: X-ray film. Using discarded X-rays from hospitals and archives, people would trim them into circles, place a hole in their center, and imprint music onto them.
Back in May, NPR published an in-depth piece on the tools used for dissent in the Soviet Union, including these records. It has several photos of X-ray records, and you can see a number of other records in the gallery below as well.
The process of making these records was briefly depicted in the 2008 Russian film Hipsters, which you can see below shortly after the two-minute mark.
All images courtesy LiveJournal user Bujhm on a GNU Free Documentation License.