Hammond organ "chopping" is an industry unto itself (making large and heavy organs into manageable and modular pieces). But, it's also easy to hack.
I've taken apart only one Hammond, but with no background and no deep understanding of electronics it was easy to see that they are well made and well suited for modification. There is a lot of room in the case, wires are neatly bundled, and the components are SIMPLE.
Of interest to this crowd would be that all the keys are simple SPST switches. From that alone, you can do a lot of cool projects!
Also of interest to this crowd would be that the organs, unlike your iPod, are designed to be opened up quickly, easily, and repeatedly.
Finally, I should point out that there is a lot of panel space to mount your own knobs (or to re-purpose existing knobs and switches).
http://tinylittlelife.org/?p=225
Screwdriver
Soldering iron
Lineman's pliers
Drill