MilkDrop is a music visualizer – a “plug-in” or extension to Winamp or Foobar2000 music players. As you listen your music in Winamp, MilkDrop takes you flying through the actual sound waves you’re hearing, and uses beat detection to trigger myriad psychedelic effects, creating a rich visual journey through sound. MilkDrop can also be driven by a live audio feed (microphone or line-in).

www.geisswerks.com/milkdrop
sourceforge.net/projects/milkdrop2
en.wikipedia.org/wiki/MilkDrop