In the 1950s and 1960s, it was common for record labels to press relatively heavy records on new or "virgin" vinyl. During the economic downturn of the 1970s, the cost of record pressing increased, and many record labels cut costs by pressing lightweight recordings from recycled materials, which contained impurities. Recycled vinyl pressings often exhibit pops, clicks, and surface noise. The process of sound transfer from magnetic tape to LP is a highly complicated process. Apprentice engineers typically spend several years learning how to become an expert in disc mastering. A mastering engineer may need to adjust and or compromise the sound quality of a record in order to maintain loudness and make the groove traceable by the stylus a record player using a low quality phono cartridge. 

Often, sounds have been mastered with additional compression, limiting, and equalization. In order to reduce wear on the master most discs are not sourced from the original master tape. The source tape used may be many generations removed from the original. Typically, the engineer cut the first pressing and a "cutting master" tape in parallel. Subsequent pressings were cut directly from the cutting master. Some pressings were even cut from copies of the cutting master tape. Each subsequent tape copy added additional levels of tape hiss, and wow and flutter, degrading sound quality. - Saulo Zucchello

"In 1977 Mobile Fidelity began to produce a line of records known as "Original Master Recording" vinyl LPs. These albums were previously released by other companies, licensed by Mobile Fidelity, and remastered by a process called half-speed mastering. During mastering, sound was transferred from magnetic tape to disc while the cutting lathe moved at half speed. The albums were remastered from the original analog master tapes, without compression, and with minimal equalization.[2] The recordings were pressed on high-quality vinyl called JVC Supervinyl, a plastic compound invented by JVC to compensate for the demands of Quadrophonic records, which had begun appearing in the 1970s. JVC Supervinyl was more durable than regular vinyl, with lower surface noise and fewer pops and clicks. Mobile Fidelity packaged their albums in heavy cardboard sleeves, inner cardboard stiffeners, and plastic liners. Half-speed mastering had been done before. Decca Records used the same process on its classical albums from 1958 to 1967. MFSL revived the practice, refined it, and made it the company's selling point. Half-speed mastering took more time than typical mastering, and it presented technical challenges. Its use was never widespread by other companies despite sonic advantages".