Piezo to contorl LEDs

Hello everyone, I've been wanting to control LEDs with audio, and I was considering the possibility of using a piezo for this task.

Have you ever done this before?

I haven't seen this done with an Arduino, but the guys over at NerdKits did this with an ATmega168, a piezoelectric buzzer used as a microphone, and a couple of external components to amplify the signal from the piezo. They drive a 24x5 LED matrix as a large bar graph tied to the sound in a room.

See http://www.nerdkits.com/videos/sound_meter/ for a video, instructions, parts list, source code, etc.

If you convert their source code to Arduino, please share it here.

The problem with a piezo is that there is not much output unless you thump it directly. As a microphone it is not very good and requires a lot of amplification to get it into a form the Arduino can take. When you say control an LED what do you mean, control covers a vast amount of projects.