When a copy is made of a music recording, it generates a music royalty which should be paid to the person who wrote that music. Thus a pressing plant ought to insist on MCPS (Mechanical Copyright Protection Society) registration and show this as an imprint on the packaging, and reputable ones do.

It is from these imprints that retail outlets inform the publisher how many copies have been sold and these are to artists.

There are, however, those producers who get round this by running off CD-R copies rather than press from masters, and these are the recordings which will not, obviously, show up on MCPS returns.