József Hajdú saved these gems for us and writes:

I felt that those X-ray record albums relate to our contemporary lives in many ways, especially when considering such terms as 'multimedia' or 'recy- cling'. I copied the X-ray films with their engraved sound-grooves on photosensitive paper and made enlargements of certain details.

Here are a few more details from another source:

"In the years after World War II, Stalin attempted to extirpate every aspect of American culture from Soviet life. Jazz, which had been played publicly in the USSR as recently as the war years, was now officially regarded as decadent capitalist filth; to even speak of jazz during this period was a criminal act...

Jazz survived in the Soviet Union in some astonishing circumstances. As jazz historian S. Frederick Starr has recounted, many of the country's best musicians were actually in Siberian prison camps, but these camps were in many cases ruled by commanders who liked jazz and who organized the musicians to play for their often-lavish parties. Prison camp commanders would even exchange these jazz groups, allowing them to "tour," as it were, camps where countless prisoners were being worked, starved, and frozen to death. Other bands were exiled to remote cities, such as Kazan in the Tartar region, where they were supposed to undergo "rehabilitation." Instead, these groups, many of which had learned jazz in pre-Mao Shanghai, took advantage of the local officials' musical ignorance, and played jazz anyway. In Kazan, the courageous bands even performed on Tartar State Radio. That's how the early stilyagi kept up with the music: by monitoring Tartar broadcasts to hear exiled musicians outsmarting their cultural keepers.

But the stilyagi managed not only to hear jazz, but to assemble collections of recordings too. How? They had turntables, but they certainly couldn't buy jazz records in record stores (there weren't any). They couldn't tape what they heard on the radio. Even assuming they could get access to a reel-to-reel recorder, where were they going to get enough blank tape? The solution was a piece of genius. A jazz-loving medical student realized that he could inscribe sound grooves on the surface of a medium that was actually plentiful in the Soviet Union: old X-ray plates. He rigged a contraption that allowed him to produce "recordings" that, while obviously of low quality, at least contained the precious music and allowed its admirers to listen to it at will. He and his imitators were to make a lot of well-earned money on the black market..."
(From In Praise of Vulgarity: How commercial culture liberates Islam -- and the West by Charles Paul Freund)

The roentgenizdat or "x-ray press" was finally discovered and made illegal in 1958; the records only lasted a few months. "Roentgenizdat" is a portmanteau word made from Roentgen and izdatel'stvo (the word 'publisher' in Russian). This word is an extension of the more frequently heard samizdat, literally "self-published." Incarceration was a common punishment for distributing forbidden music or literature. As dissident Vladimir Bukovsky put it "I myself create it, edit it, censor it, publish it, distribute it, and [may] get imprisoned for it."