Adafruit just put out a tutorial for adding pattern blinking LED lights to headphones. This instructable takes it one step further.
This project is really the Adafruit Ampli-tie project morphed into a cool sound reactive LED light appliance for your headphones. It provides a visual audio meter or color organ that responds to the volume/amplitude of the audio heard in your headphones.
Daft Punk, call me.
Step 1: Here kitty, kitty...
You can actually use any Arduino but I am using the Adafruit Flora. It is their wearable Arduino platform which I have used for many of my other ibles.
You need the microphone amplifier breakout module.
Instead of many sewable NeoPixel boards, you need to get two NeoPixel rings. A ring contains 16 RGB LED units with each pixel having its own constant current limiter chip built in. No need for external resistors. The pixel units are already chained together, individually addressable and controlled by one data pin by I2C.
A battery pack for your Flora(4.5v, 3xAAA)
Hookup wire to get everything connected.
Male header pins and female header sockets to make detachable cables.
Zip-ties and tape to put everything together
And a set of headphones you want to mod.
CAUTION: Know how to work with electronics. Use care in soldering.