Multi-channel sound and data system

A motion picture film having a photographic sound track for selective reproduction of monophonic sound when used with conventional photographic sound projection apparatus or for reproduction of multi-channel stereophonic sound when used with appropriate stereophonic sound projection apparatus, said sound track comprising:

• (a) one or more variable area or variable density monophonic recording tracks for reproduction through a conventional optical reproducer, said monophonic recording tracks occupying approximately half of the area reproduced by conventional sound projection apparatus;
• (b) two or more constant width tracks for stereophonic recordings, said stereophonic recording tracks occupying approximately half of the area read by conventional sound projection apparatus, but not reproduced by it other than as crosstalk;
• (c) one or more additional tracks for stereophonic recordings, adjacent to but outside the area read by conventional sound projection apparatus;
• (d) one or more command data tracks adjacent to but outside the area read by conventional sound projection apparatus;
• and
• (e) one or more unmodulated locator tracks at or near the extremities of the multiplicity of tracks, adjacent to or outside the area read by conventional sound projection apparatus.