Under the Copyright Act, a work is fixed in a tangible medium of expression "when its embodiment in a copy or phonorecord, by or under the authority of the author, is sufficiently permanent or stable to permit it to be perceived, reproduced, or otherwise communicated for a period of more than transitory duration. A work consisting of sounds, images, or both, that are being transmitted, is 'fixed' . . . if a fixation of the work is being made simultaneously with its transmission." See 17 U.S.C. §101. Fixation is a requirement for obtaining a copyright.