Grow bacteria on your CD for the latest sound

Want to listen to something really different? Smear yoghurt on your favourite CD. Let it dry. Slide the disc into the player. Crank up the volume. And hear that music in a completly fresh, possibly spine-chilling way.

The bizarre innovation - an "optical biocomputer" if you must know - is the brainchild of an Australian scientist, Cameron Jones, who as well as being a mathematician with a record of published research also owns a nightclub and bar in Melbourne, New Scientist reports.

Jone's pet area of research is how signals can be transmitted through biological cells, which grow in a so called "fractal" way, like three branches.

He became intrigue by experimental musicians and DJs who, from the mid-1980s, sanded, varnished or even slapped paint onto CDs to create new sounds to sample.

Music on CDs comes from tiny etched binary digits, the "0" or "1" that make up a computer code. The code, reflected back by the laser in the CD player, is then processed back into an electronic signal and converted to sound.

Mutilating the surface, so that some of the pits are missed, thus changes to sound. But Jones found that much subtler sounds could be achieved using fungal or bacterial growth, rather than scraping or coating the disc's surface.

This is because these life forms introduce tiny errors, on a micron on nanoscale level rather than the far bigger milimetric scale. In addition, the wa fungus and bacteria can shape the sound in weird ways. Bacteria grow by cell division, while fungi grow by branching. Both processes can be controlled by adding malt extract to the disc as food.

Jones told New Scientist that he came across the discovery quite by accident, when he was DJing in his bar.

"I often change CDs when my hands are wet with beer," he told the British weekly. "One night I must have changed the CDs, touched the data surface, the left them for use on another night."

The following week, he put on a CD by Nine Inch Nails and found that it would not play properly because fungus had grown on it.

But the fungus had not ruined the disc, but it would sometimes change in pitch and there were small staccato noises in the background.

He asked himself: "What would happen if I purposely grew fungi, yeast or bacteria in direct contact with the media, an manipulated their fractal dimensions?"

Yoghurt-on-a-disc was born.

Jones says that he has yet to damage any of his discs or players with his pioneering work, but warns that the technique does crash CD players on computers because the software cannot cope. Judge the sounds for yourself on (www.swin.edu.au/chem/bio/fractals/refslist.htm), which has details of his work and samples of "fractal" music. - AFP

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