I'm singing in the lair..

I was asked if it would be possible to make a device that react to singing. Initially I thought "sure, but it will require a powerfull computer, some signal processing software and complicated algorithms etc".
Somehow I couldn't shake the thought that there may be a simple way to do it.
A while ago i made a decoder for some DominoEX radio communication signals. It was a small microcontroller that took an audio signal from a radio receiver and decomposed it into its frequency components, analyzed these and turned them into data. The frequency range of this signal coincidentally corresponds to that of the human voice.

I thought that there may be a way to use part of this system to look for tones of singing. This was the idea.

I made this quick'n dirty prototype using a AVR microcontroller...

...and then surpriced everybody by singing loudly. The graph show the score*100. I think with some tweaking  it will be possible to make a simple micro controller device that detects singing.