I recenly started experimenting with the animation nodes addon by Jacques Lucke. It´s really nice and as Nicolas Priniotakis from blender nation said in his review - If you install this addon you're hooked.
For this animation I used the particle cluster nodes from the animation nodes addon
you can download the blend file here
AN experiment - force field curl clusters
Animation Node experiment - circular sound visualizer
Animation Node experiment - icosphere grow
Animation Node experiment - delayed animation