Meant for use with a RGB LED strip
MSGEQ7 and data sheet https://www.sparkfun.com/products/10468
Quick examples of it in action https://youtu.be/wdgXy7S1X4I https://youtu.be/GHSot7KyYC4
Where I got most of the info from http://www.instructables.com/id/Blinking-LEDs-to-the-Frequency-of-Musi/