Genetic Symphonies-The Building Hox of Life

Behind Building Hox: Music

Much like science, the composition process was both creative and experimental. While several variables were changed during the creation of the tune (like instrumentation, key, repetition of phrases, etc) there were a few constants I deemed critical for appropriately conveying the scientific concept at hand. These were:

• The use of 13 instruments, where each instrument represents one Hox gene group
• The progression of the music, where a new instrument is added to the tune with each subsequent button press. This represents the cumulative effect of development and helps to convey that expression of a given Hox gene group is dependent on appropriate expression of the preceding Hox group; the previous group (instrument) still needs to be active for the next group/instrument to function.
• The versatility of instruments, such that each instrument has a “unique” sound so that non-musicians can appreciate an increasingly complex and additive tune, that is due to the addition of instruments.
• The “soft” error sound, where a gentle sound does not invoke feelings of wrongdoing (like a buzzer) so that people continue to engage with the exhibit

I went through not one, not two, but 10 unique iterations of tunes applying the above principles, before deciding which to use for the exhibit. You can check out a video of some of those tunes that didn’t make the cut below. In these initial drafts, I experimented with the tempo, or speed of music, to determine the maximum speed where listeners could appreciate the cumulative instrumentation and the minimum speed such that it was not too slow so that listeners became bored. I altered the instrumentation, creating tunes with a percussive, electronic, and orchestral moods and affects. I also tried coding the idea of 13 groups/ 13 instruments into a specific number of notes per instrument. For example, Hox group 1 button sounds one note, while the Hox group 6 button sounds 6 notes.

Ultimately, I decided on the tune you hear with the exhibit because I thought it best applied the constants necessary for scientific accuracy and was most reflective of the visual aspect of the exhibit. This tune utilized instruments that had a “natural” feel to center the user in the exhibit which visually depicts wildlife; 6/13 instruments are wood-based. I also selected the tune  because I thought it was engaging and enjoyable to listen to (judging from the dancing, it seems like this was a success!).

If you’re curious, here are the instruments unique to each button/Hox gene group. Watch a video (at reduced tempo) of the score below to appreciate the addition of an instrument with each progressive measure.

• Marimba
• Timpani
• Xylophone
• Vibraphone
• Bass drum
• Hand clap
• High-hat
• Bongo Drums
• Cello
• Plucked Viola
• Woodblock
• Piano
• Chimes
• “Wrong” sound- vibraslap

Behind Building Hox: Electronics

Our exhibit would not be possible without electrical engineering, Raspberry Pis, and logic-based code. These elements are integral to the functionality of the piece and yet they are not visible to the user. Because of this, you might be wondering how a button press produces light in a specific box, or if the button press is incorrect, why there is no light, but instead an unusual sound. I promise, it isn’t magic, but rather the result of careful wiring and coding.

To understand how these pieces work together to produce specific patterns of  light/sound, let’s first meet the major players:

• Raspberry Pis- little computers that contain the logic-based code. There are two of them in our exhibit, one underneath the buttons on the podium (the sender), and one under the center most box of the art panel (the receiver).
  

• Radio Frequency (RF) Transceiver Modules– wired to the raspberry pi and are responsible for either sending signals or receiving signals.

• The code– stored on the Raspberry Pis and essentially for activation of light and sound. It contains the correct sequence of button activation and dictates when information should be sent to the receiver raspberry pi.

Now that you know the major electrical components, let’s bring it all together. In order for the buttons to make sound, or the lights to turn on, they must be physically connected to the Raspberry Pi. This is done by wiring the buttons/light to one of 40 potential pins in a Raspberry Pi. You can think of these pins as little ports/sockets associated with a specific number. Additionally, there is a pin for power and ground. The diagram to the right shows a schematic of the pins on a Raspberry Pi denoting pins that are specific for power and ground.

For example, here is a map I drew of which pins the buttons are wired to on the lights/receiver Raspberry Pi. Boxes are associated with specific pin numbers and the highlighted pins refer to those specific to ground (#6), power (#4), or connection of light source to the Raspberry Pi (#13).

Each button or light is associated with 2 wires. In the image above, the black wire is ground and connects the buttons to each other and to the raspberry pi, while the color wire comes from a specific pin on the Raspberry Pi and is associated with a specific light/ button.

Once the buttons/lights were connected to the Raspberry Pis, the Raspberry Pis could then work together to interpret the code. Each Raspberry Pi contains unique code that allows them to either send or receive signals. It essentially works like this:

1. The button/sender raspberry pi contains code in which the correct order of button activation, via pin numbers, is known. If the correct button is pressed, music is played and the RF transceiver sends a signal from the podium to the receiver/lights Raspberry Pi.
   If the correct button is not pressed, then no signal is sent to the receiver/lights Raspberry Pi. Instead, the “error” sound is heard.
2. The signal is received by a RF transceiver wired to the lights/receiver Raspberry Pi on the art panel. The code in the receiver/lights Raspberry Pi determines which pin to activate. Unlike the buttons, the light pins are all connected to relay modules. These modules are off/closed until a correct signal is received. So, if the correct button is pressed, then a signal is sent to the receiver/lights Raspberry Pi, and the code determines which relay module to “open” and allow electric current to flow through, resulting in light being turned on.
   In this video, you can observe red lights being turned on. Each red light represents the relay module (blue/green rectangles) being set to the “open” state, meaning the lights specific to that box would be on.
3. If all 13 buttons are pressed in the correct order, then the sender/buttons Raspberry Pi plays the full musical sequence, while the receiver/lights Raspberry Pi starts a countdown, that is 31 seconds long, then length of the entire musical tune. At the conclusion of the countdown, then lights turn off and the code “resets” and waits for another signal.