Two things:

> On converting metal music box discs to MIDI:

I've been doing this for awhile (hundreds of discs converted), and I've
found that nearly all discs have small, but significant, errors in
placement of the projections.

While a MIDI file produced directly from a 'scan' would be OK for
listening, the errors in timing would very likely reduce the
usefulness of the file as part of a 'searchable computer data-base'.
You probably still need a musician to edit the 'raw' MIDI file produced
by scanning a disc.

> On a computer program to search MIDI files for 'matching' themes:

My experience as a programmer (as well as musician),  suggests to me
that such a program would not be terribly difficult to write.  Probably
a labor of love, though, given the limited demand?

Jack Perron
Peterborough, NH