Most karaoke cassette tapes have the same song on both sides of the tape. One side has guide vocals and other just the background music. Many also include printed lyrics. Most DVD players will NOT play CDG discs, even if they are DVD karaoke machines. Make sure the manual states that the machine reads the CDG format.
Players play movies as well as karaoke videos with lyrics.
This is not the same as DVD, although most DVD players will read VCDs. A person, similar to a Disk Jockey, who provides a total Karaoke experience in the home or business of a contracting third party employer. Digital key change affects only the pitch, not the tempo. A non digital key controller will slow or speed up the song tempo. Guide lead vocal is recorded on one channel with accompaniment on the other channel.