THEATRE DESIGN & TECHNOLOGY MAGAZINE

1990 SPRING ISSUE - SOUND COLUMN

Reprinted in the JOURNAL OF THE MMA, JAN-MAR 1991

THEATRE NETWORKING THROUGH MIDI

By Charlie Richmond
 
 
Last year was an eventful one for networking and this year looks
to be even more so.  While FDDI, an expensive high-speed fibre
optic standard (Sound Column, TD&T, Summer '89), is gaining
acceptance, other computer network protocols continue to be
popular.  Now, a complete set of standard theatrical messages
are being developed by a variety of theatrical equipment
manufacturers who want their systems to communicate with the
outside world (and with each other).  The protocol of choice is
MIDI (Musical Instrument Digital Interface), primarily because it
has become a de facto live performance communication standard. 
Musicians have been using MIDI since 1984 to allow their musical
instruments to "talk" with each other and other intelligent
devices, primarily personal computers, using a vast amount of
MIDI-oriented software.
 
Theatre sound designers are also using these instruments and
intelligent devices to their advantage.  Even though the MIDI
sequencer software and controllers commonly available are not
perfectly suited to the impromptu nature of live theatre, the
MIDI protocol itself is easily adapted.  As long as only a small
amount of information is required to call a cue, MIDI can
simultaneously communicate such requests to several devices-such
as memory lighting systems-quickly and efficiently.  Usually,
these devices hold large amounts of detailed data in their
own cue storage areas then act upon it quickly when sent simple
MIDI "Go Cue" messages.  Usually they can both send and receive
MIDI messages, allowing flexible system configurations in which
key units can function as a MIDI translator or interpreter.  For
example, the translator may receive the same type of message from
different devices at different times yet be programmed to send
different types of messages on to the rest of the system.
 
Here are some good examples of current MIDI applications in
professional theatre:
 
-The current tour of Lily Tomlin & Jane Wagner's "The Search for
Signs of Intelligent Life in the Universe" now uses MIDI to
trigger about 50 different sampled sound effects on an Akai S950
plus longer cues on an Akai S1000 and to change six channels of
Akai PEQ6 programmable equalization on a cue-to-cue basis.  The
MIDI messages originate from the Amiga 2000 computer running the
show's Richmond Sound Design COMMAND/CUE system software
containing both MIDI cues and regular cues that control the
hundreds of faders, cross-faders and switches used to distribute
the sound in the theatre.
 
-The "Indiana Jones Epic Stunt Spectacular" theatre at the
Disney-MGM Studios Tour theme park in Orlando uses a similar
system with an Amiga 2000 to send MIDI messages to several Yamaha
SPX90II programmable audio effects units and simultaneously
receive messages from a Lexicon MRC MIDI remote control unit. 
The MRC has four sliders and switches which are programmed to
control the Grand Master and several Inter Master volume controls
on the COMMAND/CUE system's Master screen.  The MRC is a compact
low-cost universal MIDI controller which effectively gives the
operator portable live control over hundreds of channels of
audio.  Additional units could be added with a MIDI merge box to
control even more system Inter Masters if necessary, or a larger
unit such as the J L Cooper Fader Master could easily be used. 
The MRC could even send its messages over a wireless MIDI link if
desired.
 
-Finally, at the new Mirage Hotel in Las Vegas, the Siegfried and
Roy illusion show is using another similar system in a slightly
different configuration.  Rather than using the Amiga 2000 as the
central control unit exclusively, this installation allows a
two-way "conversation" to be conducted between it and the NED
Direct-To-Disk digital recording/playback system which assumes
the role of primary synthesizer and musical sequencer.  Since
many audio effects must be tightly synchronized to the music, the
NED sends MIDI time code to the Amiga, allowing the COMMAND/CUE
software to execute specific sound system cues at certain times
during musical sequences.  Conversely, the Amiga may invoke,
start, stop and synchronize specific musical or synthesized sound
sequences on the NED precisely according to the live action via
operator execution of pre-programmed MIDI cues.
 
In these ways and more, designers are finding easy solutions to
what used to be impossible problems, and they are doing it on
their own with off-the-shelf MIDI products.  Even the software
which ties it all together is already set up to handle the MIDI
messages the equipment requires, simply because the communication
protocol has been well defined and is completely standardized.
These days, it is refreshing to take two pieces of computerized
equipment from different manufacturers out of their boxes and
have them talking to each other within minutes!
 
Not content with just this and partly as a result of the
panel discussion "MIDI Mania" at LDI'89 in Nashville, several
manufacturers decided to see whether they couldn't get more
agreement on MIDI communication standards throughout the rest of
the theatre industry.  It was gratifying to see the potential of
MIDI was not going unnoticed, since many of the memory lighting
console manufacturers were in the process of adding MIDI ports to
their boards.  To be fair, a few of them have had MIDI controlled
consoles for some time but there has been a lack of agreement on
which messages to employ and for what purpose.
 
Because MIDI is a musical communication protocol it has
not been key to lighting people.  However there is a natural
potential tie-in when performers using MIDI sound equipment also
want to control lights during the same performance.
 
During further discussions with lighting control manufacturers, I
discovered that many were unaware of one or more of the
following:
 
 1.  The MIDI Manufacturer's Association (MMA) exists to oversee
     the development of MIDI standards;
 2.  MIDI is already used by some lighting manufacturers; and
 3.  A MIDI lighting standard has been proposed.
 
It seemed logical to advocate joining the MMA and becoming
actively involved in creating a truly useful MIDI communication
standard for the theatre environment.
 
As a result of this increased interest, many theatrical equipment
manufacturers have become members of the MMA and are now engaged
in developing this standard through the facilities of the
Performing Arts Network's "MMA Forum."  Involved at the time of
writing are several lighting console manufacturers from North
America and Europe, two moving light controller manufacturers, a
projector slide control designer, and a theatre sound memory
programming system manufacturer.  More of these-plus laser
control companies, rigging manufacturers, and even pyrotechnics
manufacturers-are considering participating.  The MMA hopes to
complete this process soon by receiving official approval and
adoption by the International MIDI Association.
 
There will never be a perfect communication link, since cost
always increases with performance and the cost/performance
tradeoff is different in every application.  MIDI has certainly
had its detractors, myself included, but here it seems to
embody some good characteristics and few bad ones.  To explain,
most critics have focused on one or more of the following
perceived faults:
 
 1.  Lack of speed;
 2.  Inability to travel long distances; and
 3.  Open-loop design.
 
First, it is true that MIDI is slow if one attempts to transmit
the amount of data contained within even one single sound or
lighting cue.  But that is not what we will be doing during a
performance.  Other standard and proprietary protocols, notably
USITT's DMX512, exist for this purpose.  It's true we will
develop a standard which will allow this data to be communicated
but it will be primarily used for archival, transportation or
telecommunication purposes.  The messages carried by MIDI during
live performances will be cryptic high level commands telling the
various intelligent controllers what to do or where to be within
their own frames of reference.  The longest of these messages can
be easily sent in fewer than 10 milliseconds.
 
Next, although the MIDI spec clearly states the maximum usable
distance is 50 feet (15m), this is a minimum standard allowing
manufacturers to keep costs low and products accessible to the
average musician.  Most users are aware that most MIDI products
will send and receive over much longer distances and there is no
technical reason for any limit independent of cost.  MIDI
"boosters" are common, buffering weak outputs to send 1000 feet
(300m) or more.  Wireless MIDI links are available, though they
can be less reliable than hard-wire connections.  Fibre-optic
links make very long distances possible.  Even some musical
"events" have used satellite links to transmit MIDI signals
between different parts of the world.
 
Finally, the open-loop design of MIDI, while potentially less
dependable, is probably more appropriate for live, real-time
performance applications than a network in which every message is
checked for errors, acknowledged, and perhaps retransmitted. 
Live performers would probably rather have the odd minor error
than have the entire system shut down or become unbearably slow
because the communication link has become unreliable.  Even so,
the inherent openness of MIDI design still allows sophisticated
two-way communication.  Most complex controllers can easily
be programmed to look for a highly defined series of commands. 
In the example of MIDI-controlled rigging (or anything else
requiring absolutely fail-safe operation), an operator could be
required to manually transmit a confirming "safe-to-proceed"
command over the network.  The rigging system would still
have its normal safety switches and emergency controls as well.
 
Interestingly, a new system has emerged which promises to address
all the above concerns in an even more comprehensive manner.  A
company named Lone Wolf has developed a very high speed
MIDI network called "Medialink."  It allows rapid and 
reliable communication between thousands of MIDI devices over
long distances and can configure its communication paths through
software.  This means that users will be able to interactively
define the sender to receiver matrix while the system is in
"setup" mode, yet the original real-time MIDI objective is
preserved while in the "performance" mode.  These ideas are
all valid, and, whether Medialink becomes a widely-used product
or not, the MIDI messages that are carried will always remain
compatible with any equipment available today.
 
In all, this absence of serious flaws combines with some good
unique features to make MIDI be the current choice for theatre
networking.

----------------------------------------

Copyright ©1990 Charlie Richmond