Capital J:
I think that you have a great idea however I think there ARE quite a few places already that have this kind of info. Look up info on Sony's Acid Pro app for lots of tuts and deep forum. Another very narrow niche is that of Bhaji Loops on
www.chocopoolp.com. This is a loop based app for Palm OS handhelds.
So, that said... here is my advice:
1 Create your content, but do it almost exclusively IN VIDEO! DO NOT rely on the Camtasia style, screen only with audio format but get yourself on camera! Make yourself the star in showing both yourself AND whatever gear you use in this process.
2 Create your own forum to start a community and dialogue on the site itself.
3 Find your niche by whatever feedback comes to you through those that find your content.
Now, the reason why I suggest video is two-fold.
1 As a media producer who is watching the trends, good instructional video is about to explode in the next two years. The topic you have chosen is the perfect thing to use video for in this way because of how visual it is. Trying to convey this info in text takes a highly skilled writer to accurately convey the info without confusing and frustrating the student of the material. Remember, it is confusing to them enough already in trying to learn this new music creation skill. That is why they are on your site to begin with. Don't frustrate them more by making your info harder to implement than it has to be. If you do this, you will become both GURU and HERO to your audience!
2 Video takes more effort to create the content which will automatically weed out competition from lazy competitors. What most people don't know is that the equipment needed is becoming very inexpensive for this sort of thing. If you don't want to produce the content yourself, find someone who has the gear and skills but needs more viable experience and give them part of the profit of an instructional DVD or something.
Whatever you decide, Good Luck!