Friday, April 01, 2005

Skipping the middle man

Last summer, a group of wacky composers, neuroscientists, sound engineers, and visualization researchers got together and put on a concert of music generated by one person's brain. The person did not compose the music. Rather, the person listened to some music ("Dry Mud" by Australian composer David Page), while his brain activity was measured via electroencephalogram (EEG).
The listener wore headphones to hear the music, and a cap with EEG sensors on it to record neural activity. The 26 sensor electrodes were arranged according to the 10-20 standard for EEG placement. The sensors are labelled by proximity over a regions of the brain (F=Front, T=Temporal, C=Central, P-Parietal, O=Occipital) followed by either a 'z' for the midline, or a number that increases as it moves further from the midline. Odd numbers (1,3,5) are on the left hemisphere and even numbers (2,4,6) on the right e.g. T4 is on the right temporal lobe, above the right ear. An additional 10 sensors were used to record heart-rate, skin conductance, eye movements, breathing and other data. The sensors were recorded as interleaved channels of signed 32 bit integers at a rate of 500 samples per second. The channels were separated into individually named files and converted to ascii format for simplicity of loading on different systems.

10 "sonifications" of the recorded data were chosen for the concert. In each case, the time element of the data was preserved, thus each piece is five minutes long. Beyond that, each sonification was based upon some scheme for converting the frequencies of the EEG to pitches or timbres, each scheme described in full detail in provided links. The actual sonifications --
"Neural Dialogues," "What Are You Really Thinking?" "Listening to the Mind Listening," "Untidy Mind," "The Other Ear," "Listen (Awakening)," "Mind Your Body," "Perceptions in C," "Polyrhythm in the Human Brain," and "EEG Sonification" (winner of the least imaginative title) -- are also provided in links.

I did not like Perception in C at all. The combination of randomness with shlocky string synths created a very bad imitation of minimalism. Untidy Mind is pretty cool, but my favorite is The Other Ear. It has a very Pendereckian feel, starting with slowly crescendoing clusters that build to a grand pause, leading next to scattered bursts that morph into a new type of clusters. This shows that sonification is just another means of composition, with the results dependent on the decisions made by the composer, not by the starting data set.

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