In addition to the several recent cautious recommendations I would
hint at a more brutal one, namely to dunk the bellows for a minute
or two in 40-50 degrees centigrade water to soften the glue.  This
presumes hot hide glue was used, otherwise you will have to spend much
more time using only heat and scraping.  Of course water treatment
should be completed fairly quickly to avoid notable swelling of the
wood.  Apart from being much faster this method usually leaves at
least as good surface finish as does dry work.

With smaller items, perhaps up to motors in the 1-foot range, once
you have removed accessories like cloth hold-down sticks, just drown
the whole thing.  With bigger reservoirs, etc., you should first tear
away the fabric or leather by hand and pry out any tacks holding
hinges and the like, and perhaps also break the bellows down into
parts like lids and ribs.

Once the glue has softened it is easy to mildly scrape it away together
with debris, then finish with a sponge.  Towel the components and let
dry to the next day.  The water treatment can make the wood surface a
little raw from rising fibers, calling for a light hand sanding.  The
surface will still contain some glue that is good base for gluing the
new material; there is no merit to sand it perfectly smooth.

Johan Liljencrants
Stockholm, Sweden
http://www.fonema.se/