Learn how Brett Ross powers a lavish Halloween display using MIDI
by Bryan Lanser 

It's the week before Halloween, and a line stretches down around a corner. Muffled sounds of screams drown out the nervous laughter of the people in line as it creeps forward. As you round the corner and head towards the house, the light in the trees casts an eerie shadow on the ground. You find it hard to contain your own inner-child's excitement as you near the house. You can feel your pulse quicken and spine tingle as you see an mysterious fog floating low on the ground. You peer around the corner of the display only to witness a ghastly site: a putrefied skeleton rises from his coffin as nearby a ghost floats above.

As you take in the scene, suddenly a face rises from a vat of bubbling green goo... You walk on a bit and stifle a scream as you see a man struggling to escape from a crypt, being held back by skeletal occupants. Suddenly, the music swells and a 14-foot tall grim reaper stands up, waving his arms, and starts speaking... to you. You sub-consciously take a step backwards, as it is it all terrifyingly real.

Are we at the latest haunted house at Disneyland? Or perhaps one of those terrifying dark rides at Universal Studios? No, we're in the Silicon Valley suburban enclave of Mountain View, California, home of Brent Ross, who works as at a financial advisor for most of the year. But come Halloween, he is the architect of an astonishingly realistic, fully animated display that creates massive lines that snake around the block and delights the thousands who attend. An Industrial Design major by training, Brent brings his considerable creativity to bear on his amazing Halloween displays, designing and building these spectacular haunts for the terror and enjoyment of the community. 

Occupying the entire front of his parent's house, Brent's "DC Cemetery" display has several "scenes" that allows people to view the fully animated haunts, including a music parlor, a grave site, a crypt, as well as a walk through visit to the morgue itself. Brent's spectacular spooks have become legendary in the South Bay, with a devoted following of visitors who will visit him year after year... a bit of a Holiday tradition of the spooky sort.

Brett grew up like many kids excited about the notion of a good scare. He got his start making little scenes using a black light and a bowl of dry ice fog on his porch, but soon it evolved into a black plastic maze, then a wood framed cavern, and finally the steel and wood monstrosity that covers the entire front yard of his parent's house.

Although he delights in the reaction of the people who come to see his display, the real motivation for him is the challenge of creating an original display that is better and better each year. It's a ton of work, and a huge strain on his family life, but the challenge of adding new aspects to the attraction - typically 1 or 2 new props and as many as 5 or 6 changes to the display - is simply too exciting to resist.

How impressive are his displays? Amazing enough to pocket the $50,000 first prize in a nation-wide Halloween display competition, that's how. But even more amazing is the incredible way he goes about controlling this amazingly ambitious show... entirely from a single computer... using MIDI.

Brett and his wife Kasey w/their check	A helper makes adjustments to the display

Most people think of MIDI as a music technology. And rightly so, since the "M" in MIDI does standard for Music, as in Music Instrument Digital Interface. However, many people don't understand that there are several other "flavors" and uses of MIDI that allow you to do all sorts of things, including controlling an entire show like this one. In the case of Brent's Halloween extravaganza, MIDI was something he stumbled upon one year after trying to synchronize a number of pneumatic actuators to control the motion of one of his Halloween props. A neighbor, Dave Fredrichs, stopped by while he was setting up and said "You should use MIDI for that". His initial response was "What's MIDI?" but once he experimented a bit with it, he realized that there was simply no better way to accomplish his ghoulish goals: "Dave to opened my eyes to the possibility of using MIDI, using real-time recording of musical notes and converting them into electrical signals that could then be used to turn pneumatic valves on and off. Before that day, I was hard-coding microcontrollers, something that was extremely difficult to do with multiple elements (props) running simultaneously, and then trying to sync audio to the mouth movements."

The alternatives for Brett are far scarier than MIDI: to accomplish much the same functionality, he had to use dedicated industrial programmable controllers, which would control the pneumatic solenoids using a somewhat cryptic (no pun intended) step-by-step programming protocol, entering the duration and delays of every event manually using unsynchronized timers to control the sequences, and then being left with the daunting task of locking up all of this motion to the audio soundtrack that went along with the show.

The notion of using MIDI to control physical devices is actually quite well embraced in some markets. The MIDI "Show Control" protocol supports the automation of lighting, stage effects like fog machines, and other elements of stage craft. In Japan, MIDI protocol has even been adapted to control servo control motors in robots. And it all makes sense since MIDI is really just a descriptive protocol that describes a performance event. 

MIDI describes these perfromance events by breaking down an action into separate parts: when a key is pressed on a keyboard, a MIDI message is generated that says which key was pressed (the MIDI note number / MIDI note on event), and how quickly it was pressed (the MIDI velocity), and in some cases how hard the key was pressed (MIDI aftertouch message). Some time later when you release the key, a MIDI Note Off message is generated, and any clever piece of software can easily determine the interval between the time the key was pressed and the key was released. Link a bunch of events together and you have a song... or a scare! 

This "performance description language" is what makes MIDI so incredibly popular amongst musicians - you've recorded all the "mechanical" aspects of the performance, allowing you to go back later and manipulate those aspects of the performance, fixing notes, durations, velocity, or modifying the performance by adding real-time controllers, much like going through a rough draft document and making edits with your word processor.

In the context of Halloween, MIDI is the perfect tool for controlling performance of a different kind allowing you to individually control pneumatic solenoids using MIDI messages, letting you individually control each movement as well as editing the "performance" of those movements until you have the most natural and realistic motion possible. In Brett's case, he uses MIDI on messages to close a pneumatic solenoid valve that then moves a cylinder by filling it with air from a compressor. When a Note Off message is received, then the solenoid opens and the air is exhausted, causing the cylinder to retract. By the same token MIDI messages can be used to turn on or off smoke machines or strobe lights... the possibilities really are endless, and entirely practical. 

There is another aspect that makes MIDI attractive for using it beyond the paradigm of music performance, and that is the fact that MIDI technology and tools are well understood, easy to use, and remarkably affordable. In fact, it was the affordability of the solution that intrigued Brett once he understood what it could do for him: "The inspiration to convert to a MIDI-based control system came when I had a large Grim Reaper prop sitting in the garage for 2 years. I was saving up to buy a 50 output sequential microcontroller that costs over $2000 - and it didn't have real time programming! Dave was inspired by the mechanical aspects of the prop and asked if he could "tinker" with the prop to get it running. He came back a week later with a cart loaded with a PC, MIDI keyboard, and a MIDI to parallel converter board mounted to a piece of plywood. Within an hour or so of wiring and playing with note assignments, the Reaper came to life and I was sold."

The benefit of MIDI to Brett is that it enables him to use affordable "off-the-shelf" tools to orchestrate all this magic in his award winning shows. For example, the "central command" of his show is a garden-variety PC running Steinberg's Cubase MIDI sequencing software.

Cubase software, or any MIDi sequencer for that matter, is designed to record, play, and edit a MIDI performance with extensive editing capabilities. Modern sequencers, called Workstations, also include recorded audio, turning the software into a comprehensive system for all aspects of a musical performance. Since the MIDI messages can be also used to control movements of characters instead of describe a musical performance, Brett is able to use the audio aspects of Cubase to manage the sound effects and soundtrack of the display, while using the MIDI aspects to control all the movements.

To control the hundreds of pneumatic cylinders throughout his display that make his creations move, Brett uses readily available "MIDI to Switch" technology that allows you to send MIDI messages to a relay board that closes switches in response to the particular "note on" or "note off" event. Although Brett uses control boards from a company called SD, other solutions are available such as from companies like Doepfer of Germany and MIDI Solutions in Canada.

"I recommend the SD MIDI converter boards to the point of where I now distribute their product for them on www.dcprops.com. I find the SD products are the most cost efficient and expandable of the solutions out there, and their tech support for these types of applications is far superior to others. Add to that the fact they are designed and manufactured here in California so shipping is a lot faster then the overseas alternatives. SD has also come up with a dimmer pack that expands the output so you can use it for dimming 110V lighting!"

Besides enabling him to use off-the shelf technology to control his shows, the simplicity of MIDI technology means his entire show is controlled from one rack of gear, allowing him to easily move his "control central" from place to place and store it in the off-season.

Brett's rig consists of an enclosed, wheeled server rack with a series of 1U rack mount audio amplifiers (the blue boxes in the picture), multiple surge suppressors, a rack mount PC running Windows with two M-Audio DELTA 1010 and one 410 audio card, providing 24 mono audio outputs. The cards also provide the MIDI I/O to connect to the MIDI to switch converters that control the pneumatics via 24V solenoids.

Inside the slide mount drawer that houses the MIDI to Switch converter boards that provide a total of 256 24V DC outputs to drive the pneumatic solenoids, all powered by a 20-amp 24V DC power supply and battery backup power source. That was particularly important in the old days when we were blowing breakers every 20 minutes due to the overloading the electrical circuits with too much lighting and air compressors!

Even though Brett doesn't use MIDI for making music, it certainly empowers his creativity while providing a reliable, cost-effective solution that delights the community year after year: "In my opinion there are many advantages to using MIDI, starting with giving you a centralized control hub and letting you easily perform a looped show. MIDI provides cost effective expansion capabilities, and the excellent real-time control provided by sequencers like Cubase combined with an easy to use interface makes programming the show very easy. Add to that the fact I have control over all aspects of automation and the soundtrack with support for multiple channels of audio and you can see why MIDI is a great solution for me.

There are challenges though. Comments Brent: "Since MIDI is designed to make use of a musical keyboard, using regular switches to trigger MIDI events is difficult, although he is working with SD Designs to create a "Switch to MIDI" converter to use on the show. Also, since the workstation sequencer runs on a computer, there are the standard issues of using a computer that presents its own set of issues when compared with the single-purpose industrial controllers. This is because no computer is ever as stable or reliable as a dedicated hardware device, but in this case the versatility of MIDI + audio makes up for it."

MIDI may be a little scary to some people, but with a little effort you can easily learn to exploit all the power and convenience this technology has to offer. However, for some people, MIDI will always be scary, especially when it is enjoyed in the form of a remarkable Halloween display in Northern California. Cue the lightning sounds... and be aware of what lurks in the vat of bubbling ooze...