this will allow you to use a photocell / photo resistor to control your synth with light. i use an 1/8" jack for the photocell and have it on the end of a long cord. be careful though, if you mount the jack to an aluminum panel you will be grounding out the photocell--i use a plasic panel for this module.
i like sticking the photocell to a TV screen. a little bit of slew / lag afterwards can help smooth it out if the sound is too grainy.
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