liner note 
noun (usually liner notes)
The text printed on a paper insert issued as part of the packaging of a CD or on the sleeve of a record.This kind of thing can be found on any CD liner note....
- We get extensive, data-packed liner note essays by Tim Scott in every package.
- By the way, I bought the soundtrack and a liner note by Helgeland gave a pretty cool explanation of why he chose rock-n-roll for the soundtrack, which is in fact excellent.