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New Tricks for an Old Dog

October 1, 2006

For more than 20 years, the main purpose of MIDI has remained much the same: triggering sounds on a synth or sampler. Yet MIDI's modest-bandwidth, straightforward instruction set makes it useful for a variety of other situations, both musical and nonmusical. In this article, I'll explore some alternate uses for MIDI that you may not have considered. You'll be surprised at how useful and powerful this old pony can be.

State Your Meaning

The vast majority of MIDI messages fall into the category of Channel Voice messages (Note On, Control Change, Pitch Bend, and so on) and are typically intended to generate a sonic response from a device. But Channel Voice messages can also trigger nonmusical events. Using a program such as SubtleSoft's shareware MidiPipe, Mac users could map a MIDI message from a footpedal or a particular key on a synthesizer to trigger an AppleScript that advances a Keynote slide show, thereby controlling both the music and the visuals simultaneously.

FIG. 1: The LanBox-LCX theatrical controller can send and receive messages in the DMX lighting protocol or in the MIDI protocol. It can be connected to a computer via USB or Ethernet. Photo courtesy of CDS advanced technology bv, NL.

Even more flexible are programs that can translate incoming MIDI messages to key combinations that can be read by any software on your computer. Mac users can do this with Charlie Roberts's freeware midiStroke, and Windows users can use bome.com's inexpensive Midi Translator. With either of these, you could use any MIDI control device to start or stop a QuickTime movie or change its screen size. You could even open a Microsoft Word document from your keyboard and have an audience see the name of your band or the current song title displayed on a projection screen. The possibilities are endless.

On with the Show

MIDI System Exclusive (SysEx) messages allow instructions to be sent to a specific device rather than to all the MIDI devices networked in a studio. One group of SysEx messages is called MIDI Show Control (MSC), which was created to control theatrical lighting and effects devices. For example, if you have a sequencer playing music while dancers perform, the sequence could also contain SysEx commands that change the lighting or start a fog machine in sync with the music.

A popular piece of hardware used for this type of control is CDS advanced technology's LanBox-LCX, which can understand MIDI messages as well as DMX data, a common communications protocol for theatrical lighting consoles (see Fig. 1). The LanBox-LCX acts as a middleman between a MIDI controller and the show's lighting and effects devices. It gets programmed with a series of cues and specific instructions for each. During a performance, stage managers can use the controller to step through a show by simply pressing an increment button to run through the cues.

There are also times when you can use a standard Channel Voice message for an unusual purpose. The textbook example is a dramatic scene in which a character smashes a bottle on a table. The bottle has been prebroken by the props master so it can be reassembled and resmashed for every performance. Unfortunately, this prop makes a pathetic sound when it is rebroken. With an ineffective sound, the action looks downright silly.

But a remedy is available that involves a transducer, which can translate an electrical impulse, and something that can translate that impulse into MIDI. One such device is the MIDI Solutions Relay, which can be attached to a garden-variety transducer that is embedded in the table surface. When the bottle strikes the table, the transducer sends an electrical trigger to the Relay, which in turn sends a Note On message to a sampler that plays a shattering-glass sound effect through a hidden speaker onstage. The sound effect, directly triggered by the action, makes the scene look exciting.

Control Issues

MIDI Control Change messages carry constantly changing streams of information, such as the position of a slider or pedal. Each controller is identified by number and channel. With 16 MIDI channels having 128 available controllers each, there are 2,048 discrete streams available. Some keyboard controllers have standard assignments; for example, a mod wheel typically transmits Control Change 1, and Control Change 7 usually sets a channel's volume level. But strictly speaking, the device receiving the information doesn't care what sent the stream, and the device sending the stream doesn't care where the stream is going.

Synth Zone (www.synthzone.com/ctrlr.htm) lists a delicious smorgasbord of quirky and innovative control devices. The BodySynth, for instance, created in 1996, is a bodysuit embedded with MIDIfied sensors. A performer's gestures and movements are translated into MIDI Control Change streams that can be mapped to any MIDI program or device, which can in turn do anything in response. For example, extending the right arm might cause Cycling '74 Max/MSP to trigger a flurry of notes, while rotating the extended arm to different angles might change the speed of the flurry.

Three-dimensional rendering programs such as Autodesk Maya allow artists to create sophisticated and dynamic animations controlled by MIDI. Motion capture devices like the BodySynth are familiar to movie animation studios. For a film like The Polar Express, the characters were rendered by computer graphics, with the motion driven by Tom Hanks and company performing in bodysuits covered with sensors.

The Vision Thing

Another common use for MIDI controllers is real-time video processing, where Control Change messages are mapped to video parameters (luminance, clip selection, playback speed, effects, and so on), allowing video artists to create improvisations intuitively by just riding the knobs and faders of their favorite control interface. Most VJ programs are similar to Max/MSP in that they are graphically oriented, with processing operations represented by icons that can be freely connected to create customized patches. A video clip, for example, may have its frame numbers mapped to a MIDI fader. Familiar DJ scratching effects may be applied to the video clip by quick fader moves.

FIG. 2: Resolume VJ software allows customizable real-time video improvisations.

One tier of video-processing software includes the Jitter objects for Max/MSP, ArKaos VJ, and Vidvox Grid Pro. These are complete programming environments and tend to be used by programmers to create intricate and individualized patches for venues like art galleries and computer music festivals. VJs, who tend to play different venues night after night, gravitate toward programs like TroikaTronix Isadora or Resolume (see Fig. 2). Though they may not be quite as open-ended and flexible, they have an easier learning curve, can handle large clip libraries, and are robust enough to be put through their paces for an 8-hour rave.

Laptop video software and MIDI controllers have simplified VJs' lives enormously. A few years back, VJs needed a truck or van to transport multiple desktop computers, audio and video tape decks, CD and DVD players, and audio and video mixers. Now they can get to gigs by subway, carrying just a laptop with their software of choice, a MIDI interface, and their favorite control surface.

Don't Raise the Bridge, Lower the River

Dense streams of control information can get bogged down by MIDI's serial message stream at the slow transmission rate of 31.25 kilobaud. But communications can get a boost if data is delivered over computer networks via the faster Ethernet. Virtual MIDI cables, each transmitting 16 channels, can be created in programs like MusicLab MIDIoverLAN CP. A single computer can act as the master controller, sending synchronized commands over a network of computers, each of which might be doing a different task — one might be sending commands to a MIDI synth, another could be running a sequencing program, while another could be generating animation or processing live video. Even if some receiving devices can't respond faster than MIDI's baud rate, at least the computers that control them get their information delivered much more quickly. Thus, though the speed limit can't be raised, Ethernet can at least widen the MIDI highway.

Is MIDI rudimentary? Yes, but it's easy to implement on just about any kind of device. Remember the wisdom of handyman-comedian Red Green, who uses duct tape to fix everything. MIDI, though crude, can hold everything together. It is the duct tape of multimedia production.


Mark Ballora teaches music technology at Penn State University. Special thanks to Curtis Craig and Gavin Burris (aka VJ86) for their MIDI-controlled insights.

MANUFACTURER CONTACTS

ArKaos www.arkaos.net

Autodesk www.autodesk.com/maya

bome.com www.bome.com

CDS advanced technology www.lanbox.com/products/LCXDataSheet.html

Cycling '74 www.cycling74.com/products/jitter.html

MIDI Solutions www.midisolutions.com

MusicLab www.musiclab.com/products/rpl_info.htm

Resolume www.resolume.com/features/index.php

Charlie Roberts www.charlie-roberts.com/midiStroke

SubtleSoft http://homepage.mac.com/nicowald/SubtleSoft

TroikaTronix www.troikatronix.com/isadora.html

Vidvox www.vidvox.net

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