Big harmonicas

I picked up the harp (diatonic) about 6 months ago and
I love it. However, it's not just diatonics that I'm
interested in. Browsing through on-line catalogs, I am
facinated by all kinds of harps and I wonder what they
sound like and their application.

I live between Milwaukee and Chicago (a fairly
metropolitan area) and I still have to travel 50 miles
just for diatonic lessons. I'm wondering how one
learns to use the more obscure chromatic, double reed,
or orchestral harps? 

Can anyone clue me in?

Rusty