Hi Magica Alfa.

You don't need to have a professional video camera. You just need to record the Audio directly into your PC and replace what the camera mic picked up with the quality recording.

Heck, the MediaStation itself can do this so that would be a really cool way to make the video.

Here's me playing a KORG M3 live, the piano is only used as the controller.
Hi Quality DIVX 7 http://www.irishacts.com/video/cainteach.divx

Or Low Quality YouTube. http://www.youtube.com/watch?v=gGwH7E_fn6c

The sound quality of my YouTube is still better than anything uploaded by Lionstracs and that was me just messing around at home.

Regards
James.