Prince’s “Crystal Ball” is a three-disc set that was released in 1998. It consists of previously unreleased material, including demos and outtakes from the “Purple Rain” and “Batman” movies, as well as several new tracks.

The first disc is the “Purple Rain” demos, which were recorded in 1983. These recordings were made before Prince had signed with Warner Bros. and were intended to be given to the studio as an audition. The tracks include early versions of “Purple Rain,” “I Would Die 4 U,” and “Baby I’m a Star.”

The second disc is the “Batman” demos, which were recorded in …