This is a metalworking project more than a musical project.  One good
place to start is to sign up with the Usenet group:
rec.crafts.metalworking.  I haven't had a look at it for almost a year,
but it was always the finest newsgroup for amateur metalworkers extant.
There are also several horology newsgroups as well.

You'll have to spend some time learning about both music boxes and the
techniques of clockmaking before you can properly define your problem.
You might, for example, wish to eliminate much of the gear train by
driving the pin barrel directly with a slow-speed motor, such as a
stepper motor.  This gets rid of most of the clockmaking and
mainspring work.  Some of the miniature work involved in making the pin
barrel itself can be avoided by using a big punched disk, like those
on the Thorens boxes.

More ideas:

I'd suggest making your first music box as large as you can.  How about
a four-foot diameter wood drum on which you mount pins (sheet-rock
screws?) that actuate microswitches?  Each microswitch could control a
single circuit that would hit a properly-tuned bell, reed, or
electronic oscillator.

This sort of approach would teach you how to arrange pins and make
chords, etc.

M Kinsler

You'd need one hell of a snuff box to fit the thing inside, though.

Lancaster, Ohio
http://www.frognet.net/~kinsler