Know those records that you insert into a vinyl record player? Basically those, but pirated since a real one costs money when you purchase them at official music retailers. It involves the process of obtaining a legal copy then using wax molds (to recreate a record) and specialized tools (prevent quality loss) duplicating the record. (Also, “Bone Music” existed in the Soviet Union by printing music by using x-ray films).
At least some of my blues collection would have been ripped from record in the late 90s and early 2000s. much of the great music of the early 20th centry never offically made it digital until very, late if ever
but I’ve never heard of wax discs being used en-mass