[sdiy] A few Oberheim questions

[David Cornutt]

Please humor me for a moment, for I have sought the answers
to these questions via Google but haven't really come up with
any definitive answers.  I'm trying to write a patch editor and
librarian for the Matrix-1000 and I've run into some questions:

1.  I have a request to make the editor also support the
Matrix 6/6R synths.  Can anyone summarize what the differences
are between these and the 1000?  I know that the 6/6R support a
keyboard split/layer mode that the 1000 doesn't have.  What else?
I see some references in the Matrix 1000 programming info to,
for example, an "external" trigger mode for the LFOs.  Is this
perhaps a leftover from an external input on the 6/6R that
the 1000 doesn't have?

2.  Other than the fact that one is a keyboard and one is a rack,
are there any differences between the 6 and the 6R?

3.  The Matrix-12 doesn't really fit into this line; it's more closely
related to the Xpander than it is to the Matrix-6.  Correct?

4.  While I'm at it, just what are the "15 filter modes" on the Xpander?