More transparently, there was once a whole label devoted to issuing pirated LPs in the US taken from shortwave radio tapes of BBC broadcasts of obscure modern music. They were issued as by imaginary performers with extremely bland names, but I doubt that anyone knowledgeable enough to want the music was fooled, as most of the works had only ever been performed once, on those BBC broadcasts. The only people who seem to know or care much about this business are discographers of some of the more frequently-heard composers.

Ah yes, Aries Records. This actually began as a label named Phorion (you may get the joke even if you're not familiar with Lukas Foss' "Baroque Variations"), which released one LP of concert music by Erich Wolfgang Korngold, which in 1971 was something of a rarity on disc. The uncredited recording of the Cello Concerto turned out to be the one that Charles Gerhardt and his RCA crew already had "in the can," so Phorion vanished without a trace, and Aries appeared in its place.

The lifted BBC performances included a number of symphonies by Havergal Brian, disguised with pseudonyms, including the premiere of the 28th symphony as conducted by Leopold Stokowski (a 90 year old conductor premiering a symphony by a 90 year old composer, or nearly, as I recall). John Canarina wrote an angry article for High Fidelity about how his performance of Symphony #25 had been filched by the label.