An editing convenience which lets you record a new soundtrack, while keeping the existing video portion of the tape as it is. (Only the linear mono audio track can be replaced — the HiFi soundtrack can't be re-recorded without erasing the existing video.)

Adding voices, music or other sounds to videotape.

The adding of additional audio (e.g. music) to a soundtrack

Add your own commentary or soundtrack to the footage.

For adding soundtracks such as narration or music to previously recorded material on stereo video tape. Useful when editing camcorder material.