(1) To mix sounds from a non-sync source into the live sound for a TV show, or into the mix for a videotape production or spot. One may fly in a narrator, Foley, etc. (2) To record sections from one or more tracks of a multitrack tape onto a second recorder (generally a two-track), then copy them back onto the multitrack in another section of the performance. For example, one might take the background vocals from one chorus and fly them into another section of the song. Short fly-ins can be done without SMPTE sync, although it is somewhat difficult.