Singing. Is the following possible?

Singing, something I’m sure we all like to do when no one’s around. (-:

So I wanted to make a mini game for my game…
But is the following even posible…?

I have a microphone, and 2 MP3’s.

One MP3 as music on it, the other one has Lyrics (the singers voice)

The MP3’s play at the same time, only the voice level is 0.

Speaking in the mic will make the voice level raise acording on how loud you speak/sing/scream.

So, when you’d wisper in the mic, the voice will be very quiet…

But if you’d scream in the mic, the voice will be loud.

…But, is this posible?

If so, help me on the trail a little? ^^;