Peter Kirn makes music with an unusual instrument - his own body.
The Kentucky native pinches two electrically charged pennies connected to a laptop via two short green wires.
The rudimentary contraption is held together by bits of solder and hot glue which allow him to measure the electrical currents of his body and synthesize them into melodic sound.
Kirn, 34, a writer of creative technology, is one of several artists performing in Berlin who are exploring new ways of composing music with the human body.
"As your mood changes, the skin responds because it is part of the same system as your brain, which controls the pores of your skin," Kirn told Reuters.
Fluctuating sweat levels affect the skin's ability to transmit electricity, a characteristic Kirn calls "galvanic skin response".
But Kirn's technique is just one way to tap into the human body's musical potential.
Marco Donnarumma, a 27-year-old teacher from Italy with a passion for live music, tunes into the sounds muscles make when they move. Listeners can literally hear the friction of tissue as it expands and contracts.
Using a sensitive microphone to amplify the low frequency sound waves a muscle emits when it is flexed, Donnarumma has learned how to produce actual rhythms by simply moving his body.
"In the beginning, for instance, I was just standing with my legs still and waving my arms," Donnarumma said. "Now I completely involve the whole body in the performance."
His song "Hypo Chrysos", for example, sees Donnarumma tie two concrete blocks to his arms - an idea inspired by Dante's classic poem "Inferno" in which the poet encounters sinners in hell wearing cloaks filled with lead. The extra stress gives off a dry, crackly sound.
The technical term for listening in on the body's internal functions and converting them into melodies is "musical biofeedback", according to Claudia Robles Angel, an audiovisual artist from Colombia who played a concert at Berlin's Leapknecht sound lab alongside Kirn and Donnarumma earlier this month.
Robles's specialty is using a so-called electroencephalogram, or EEG, to measure her brain waves while forcing her mind from a state of calm to one of utter stress, a feat she says is accomplished through breathing and meditation.
Sensors inside the device, which resembles an open helmet, relay the data back to a computer which then reprograms it into music.
"With this kind of bio-device you become more aware of your body," Robles said. "That's really how I can change my mood."
Complete relaxation is also what Kirn said produces the richest sound. He found that the more he tried to control his thoughts, the plainer the music became.
"If you too heavily try to think about what you're doing or apply intention to what you're doing, you can short circuit your own creative process," Kirn said. "The paradox of the brain is it thinks best when it's not really thinking."