One of the last assignments of the semester for the students at the Université de Franche-Comté, in the Master's program for multimedia - music & sound option , consisted in the study of a mystery box providing live sound processing. The students were given an audio connection to the input & output to the box, and were to determine its function. The students came up with clever ways of exploring the box, feeding it with sinusoids, musical sounds, or a-periodic signals. They also listened to the output of the box with "no input" (i.e. low level noise). Here is an example of a screen shot included in a student's report. Sonogram of the output of the mystery box, fed with "silence" (left) and a 500 Hz sinusoid (right). The students were free to use the tools of their choice. Mostly, they used Logic or Audacity to feed and record signal, and Sonic Visualiser to analyze the sounds. Looking at the sonogram above, what kind of processing does the my