Mixed-mode CD 
A CD-ROM format, developed in the mid-'90s, that combines data (Yellow Book) and music (Red Book). Data is always stored in track 1 of the disc, and music is stored in tracks 2 and upward. Skipping track 1 was essential, lest a nasty noise come out of your speakers; users had to skip the track manually at first, but eventually CD players did it automatically.