Apparatus for electronic recording of sound; Apparatus for reproduction of sound; Apparatus for the reproduction of sound; Media for recording sound; Media for the reproduction of sound; Music centres incorporating sound and video recording and reproducing apparatus; Optical sound processors for motion picture soundtracks; Portable sound reproducing apparatus; Sound amplifiers; Sound mixing apparatus for the broadcasting of theatre sound; Sound processors; Sound record storage apparatus; Sound reinforcement apparatus; Sound reproducing apparatus; Television apparatus incorporating sound reproducing apparatus; Video recording apparatus incorporating sound reproducing apparatus; Video recordings incorporating sound track