Fabian Oefner:
What you see on these images are color pigments dancing on a speaker. By placing the pigments on a speaker and then playing music through it, the membrane of the speaker starts to vibrate, creating these funny looking figures. To capture the very moment, in which the pigments are lifted into the air, a microphone was attached to the flash system. Like this every time the micro picks up a sound, it triggers the flashes.
These are pretty awesome photos. Oefner also gives a behind-the-scenes look at the project.