Different categories of definition have been found as regards the use of MOS. MOS is used mostly when a scene is filmed without sound. A Hollywood actor defines MOS as “Mit Out Sound” while some people refer to it as Motor Only Sync. It is called a standard film jargon abbreviation by some people and it is used during film production to indicate associated film segment that has no audio track.
When sound is omitted while recording a particular shot, it saves a lot of time and relives the film crew of certain requirements. For example, silence during a take. This is what makes MOS common during film shoots when some subjects of the take are not making any speech or otherwise generating useful sounds
MOS take is always being combined with miscellaneous sounds recorded on location in post-Production, the musical sound track, voiceovers or sound effect that is created by a Foley artist.
Origin of the term
Different sources have emerged as regards the source of the abbreviation MOS. During recording when the sound recording reaches the point where the sound is recorded on a synchronized but separate piece of media i.e 35mm film, audio tape or other media, keeping the camera film and recoding in sync MOS will be needed. The solution that arose was only to use a special form of motor with multiple windings in it that has the capacity to connect to another motor in such a way that turning one motor to a certain distance will turn the other exactly the same distance. With appropriate circuitry the motors does not necessary need to be together and they do not have to be of the same power size. For you to use this system, the sound mixer will need to connect an intercom to the sound records to roll or start the system
The recordist who actually started and stopped the camera motor had a switch in other to ensure the camera didn’t roll at an inopportune time. For example, loading, replacing lenses. E.t.c and to put a stop to it whenever the need arose.
The sound booth is where the actual power source of the camera is located. If a shot is planned that does not necessarily require sound, the sound mixer will go to work asking the recordist to roll the motor only. The recordist will take action starting the camera motor without necessarily starting the matching electronics and motor. This procedure is what brought about the name Motor only Shot (MOS).