Continuing the exploration of light-driven sound, the second demo is a tiny "piano". Instead of controlling a continous noise, each phototransistor is turned into a pinao "key". And the shadow, the inverse of light, is used to trigger sounds when fingers obscure the sensors.
Limited by the number of phototransistors, I set the frequencies to that of the five notes Do, Re, Mi, Sol, La, the pentatonic scale of classical Chinese music.
An interesting feature is that since the sensor readings are analog, I can control the loudness of the sound as my finger gets closer to or further away from the sensor, allowing for some sublte effects. This makes the "instrument" somewhat closer to a real piano, than say, a computer keyboard.
You can view a video recording of the demo below: