Selective synchronization. (1) In a multitrack tape recorder, the use of the record head to replay material from other tracks to be heard by the musicians while they overdub a new track. This is essential for accurate synchronization as the extra few milliseconds afforded by its position will compensate for the inevitable delay if the signal was taken from the main replay head which is some millimeters farther down in the tape stream. When the tracks of a multiple-track tape recording are recorded sequentially, one must listen to the previously recorded tracks while the current one is being recorded. If the standard playback head is used for this, there will be a time delay between the tracks when played back because of the physical distance between the recording and playback heads in the machine. To solve the problem, the record heads of the previously recorded tracks are used as playback heads while the adjacent tracks are being recorded. Since all the record head tracks are in line, there will be no delay. Also called simul-sync. Ampex has trademarked Sel-Sync,”, but other products have similar features. . The replay quality is less good when using the record head for a function for which it was not designed, thus it is important that the recorder returns to monitoring from the main replay head during mixdown. See auto-input. (2) The process of recording new tracks on a multitrack tape while listening to previously recorded tracks via playback through other channels of the record head.(2) On a recorder used for synchronization of sound with motion pictures or videotape, a separate sync head that records and plays the sync tone or other sync signal.