I tend to find most listings for instruments under the "Other"
subcategory of the "Piano & Organ" category within "Musical
Instruments."  I don't know where I would recommend listing an
instrument that is neither a piano nor an organ (such as a Violano)
but I believe there is also an "Antique Instruments" category.
Any parts might belong in the "Parts & Accessories" subcategory
of "Piano & Organ."

I have rarely found a music roll listed outside the "Player Piano
Rolls" subcategory of "Piano & Organ."  While the title of the
subcategory is not correctly descriptive of all music rolls, they
seem to all be found there.  Of course, some of the best deals I've
gotten have been on music rolls listed elsewhere.  I once found
an absolute steal on a style 165 roll, for example, which was listed
as "calliope circus music box scroll" or some other such nonsense.

In general, I would say that, in order to be found easily by a search
engine such as those on eBay, it is important to understand search
algorithms and how they are employed.  There are several illuminating
articles which can be easily found, ironically, on Google.  Basically,
choose several relevant "keywords" and repeat them throughout the
listing.  If these "keywords" occur with sufficient frequency and are
fairly specific, a listing will rise to the top of the results.  If the
"keywords" one chooses are too general or vague or appear only once or
twice, a listing might be lost in the shuffle regardless of which
category it has been placed in.

TJ Fisher
Washington, D.C.