Gijs writes:

This sequencer scans images, and plays the image as midi notes. It uses LDRs to measure the gray-scale of specific point of a image, and triggers midi notes from a selected threshold. When the threshold is reached the velocity will be set by the darkness at that point. the darker point the higher the velocity will be. The sequencer has 24 LDRs that are read into 3 ADC ports of the arduino, via 3 4051 ics.

Via Adafruit.