We've seen a number of weird and wonderful musical creations here at Gizmag but we have to agree with the creator of the hipDisk when she describes it as possibly the most undignified musical instrument ever. This strange interactive sonic system is made up of a pancake tutu-like disk at the hip and another above the waist which cause a sound to be generated when the two disks meet at specific points around the edge. In order to get to those points and create simple monophonic tunes or melodies, the wearer has to twist, turn, bend or stretch so that the two conductive contact points meet.

The first hipDisk prototypes were designed and created by Danielle Wilde over a three week period towards the beginning of 2007 at Reskin, an ANAT Emerging Technology Lab workshop set up to explore attributes and potential uses of conductive fabrics and inks in wearable applications. Designed to get people moving, the wearer is rewarded for a particular body movement with one of 12 notes from a chromatic scale. Some extreme choreography can result in simple, stylophone-like musical compositions.

The device is made up of two large polypropylene disks - one attached to the torso, just above the waist, and the other to the hip. Lycra tubes filled with cotton braid and wadding are mounted on the inner faces of the outside edge of each disk. These are home to twelve on/off switches constructed using fabrics with conductive qualities. Each soft switch represents a note in a chromatic scale and is made from two layers of conductive fabric sewn together with conductive thread, and placed at equal intervals around the edge.

Early conceptual experiments included weaving conductive thread into channels that could be positioned next to the torso and measure its bend, and the development of small wing-shaped devices that extended out from the body, to obtain similar measurements. Such investigations were concerned only with the body's movement along a single axis and abandoned in favor of a system which offered more than simply raising arms or bending from side to side.

At the center of each disk is a plastic band - one for above the waist and one for the hip. The upper band features two plastic boxes containing a Basic Stamp 2 micro-controller, a battery and an amplifier. Aluminum strips offer some reinforcement and help maintain a perpendicular relationship between the waist- and hip-bands.

As a user bends or twists into a position, a soft switch on the upper disk comes into contact with its opposite on the lower disk, completing the circuit and producing a quite primitive audio output from a speaker mounted within the bodice of the wearer's costume. When the creator demonstrated hipDisk at Reskin, she found that the cleavage of the wearer could actually serve to enhance the performance of the speaker.

The switches are programmed so that the front center position produces a middle C note and then descend through the scale in an anti-clockwise direction. Users can remember note positions by visualizing each one assigned to a number on a clock face and can then follow a preset pattern or routine to create a simple tune or melody. Like many instruments, novice users should be able to master simple tunes relatively quickly but seasoned twisters may well be able to learn more complex compositions.

Mentally and physically demanding

While not specifically designed as an exercise aid, the creator found that a good deal of effort on the part of the wearer is needed to generate something more than an annoying 1980s mobile phone ringtone sound. As the tempo of a hipDisk composition is wholly dependent on the wearer's ability to move from one position to another in a timely fashion, the desire to trigger the correct sequence of sounds can result in the user pushing the body into otherwise unexplored physical positioning. Such physical engagement can lead to the development of core body strength and physical flexibility.

Wilde says that users of the device invariably have a smile on their face when bending, twisting and stretching to create a tune. Whether this is due to unbridled enjoyment or an attempt to mask absolute shame is difficult to judge but hipDisk wearers may well be in for a shock when they first encounter a smartphone video or photo of their bizarre performance.

"The first time I presented the hipDisk I was shown a short piece of video footage of me performing and I found it shocking," says Wilde. "I had truly had no idea of how I behaved physically and how unconventionally unconstrained I appeared to be (and in fact was) when wearing the device. I was embarrassed to see myself so exposed, unfiltered. I burst out laughing as did the people around me who had seen the performance and/or could see the footage. Later, I experienced a similar sense of shock when I saw photographs of me performing."

As seen on TV

The designer has since formed a four-person group of hipDiskettes to gain a better understanding of complex chord and harmony production, working on a combined rendition of The Girl From Ipanema. She has also sacrificed the Basic Stamp 2 micro-controller in favor of an Arduino-bootloaded AVR (that's said to be much faster with much less perceptible lag), is now using MDF boards and says that the device is now adjustable.

The hipDisk device recently made an appearance on Australian TV in ABC's New Inventors show, emerging victorious as episode winner.

Wilde says that upon completion of her PhD in August, she intends to make hipDisk available in kit form so you may well see the device adorned by groups of fun-seekers looking for a new way to keep trim. Availability information and pricing will be posted on the project page of her website.

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