The music industry uses a digital communication protocol known as
MIDI
(Musical
Instrument
Digital Interface). This was originally designed to allow musicians to link their instruments, for example to play one synthesizer and have it operate additional synthesizers or other electric musical instruments. This eventually expanded to include other devices, so that a modern composer can program his or her piece into a computer, link the computer through
MIDI
to various instruments, and by triggering the computer cause the piece to be performed just by pushing a button. Many modern lighting computers, especially rock and roll boards, have the ability to receive and transmit MIDI. Thus a
MIDI
command can trigger a light
cue
or sequence of cues, allowing the musician to control the lighting - not necessarily a lighting designer's dream. Conversely it means the
lighting board
could trigger a sequence in the music, or any effect which responds to
MIDI
commands.
MSC Until recently,
MIDI
has been used in multimedia shows to ensure synchronization between the various technical systems. A computerized show
controller
can emit a command which will simultaneously operate lighting, sound, and other production elements, all of which are capable of receiving
MIDI
commands. However, standard
MIDI
commands are not convenient for such a purpose since they are tailored to the needs of musical programming and performance rather than for show control.
In 1991, the
MIDI
Manufacturer's Association adopted a variation of the
MIDI
protocol called MSC -
MIDI
Show Control. This protocol is intended for controller-to-controller communication in complex shows. Each
controller
communicates with its devices with its own appropriate protocol - for instance the lighting computer sends DMX512 to the dimmers, while the
projection
control, video, pyrotechnics, scenic machinery, each use their own
control signal
protocols (SMPTE for instance). A main coordinating computer sends MSC commands to all of these controllers, each of which receives its MSC command and then uses its own protocol to operate its devices.
Centralized
show control
is a rapidly developing field. A modern musical, for instance, might involve a variety of devices which must be operated in absolute synchronization for safety as well as artistic considerations. Scenic machinery, pyrotechnics, moving lights, and video walls must all be controlled with precise coordination. More and more entertainment configurations involve a central computer controlling a wide variety of control boards through
MIDI
or MSC signals. Each
control board
must be capable of responding to the show controller's
MIDI
or MSC signals and then manipulating the devices under its own control, using its own communication protocol.
MSC is a fairly new protocol and many controllers do not yet support it.
