The Colorganic Spectralizer is an audio spectrum analyzer with seven bright 10 mm colored LEDs. Use it as a miniature color organ or just a flashy desktop display thingey. Each LED responds with a brightness that's in proportion to the sound level at a particular frequency. The Colorganic Spectralizer comes complete with an integrated microphone and runs for hundreds of hours on one set of AA batteries.
This is the sturdiest version of the Colorganic Spectralizer. Although not recommended, it can usually take a drop from 4' onto concrete without significant damage.
This is a hackable gadget! The design files are published here (see the Resoruces section below), and you can modify the source code and reprogram the device. There's even a Bar Graph LED modification that you can build and add on to make your Colorganic Spectralizer look like a graphic equializer display.