Hacham Bension Abba Shaul (Israel, 1923-1998), in his work Or Lesion (42:7; listen to audio recording for precise citation), discusses the interesting question of whether one is allowed to speak on Shabbat if his voice would be recorded by a recording device. If there is a tape recorder or disc recorder turned on in the room, is one allowed to speak, or must he ensure not to make any sound so that he will not be recorded on Shabbat?
Hacham Bension rules that producing sound which will be recorded is forbidden on Shabbat. Although it is not considered "writing," as this is not the normal way things are written, it is nevertheless forbidden because of a different Shabbat prohibition "Tikkun Mana," which means "completing a vessel." An empty cassette or, in contemporary terms, an empty disc cannot be used for the purpose for which it was designed, and it is thus considered incomplete. It is only once material is recorded onto it that it becomes functional, and therefore recording sound is forbidden on Shabbat, just as it would be forbidden to make the final touches on a new utensil. Although we normally associate the Torah prohibition of "Tikkun Mana" with physical work on an object, such as hammering the final nail, it applies to any form of "completion," and thus Hacham Bension rules that one may not record his voice on Shabbat.
