Thank you all for your most helpful responses!

Yes, indeed, rebuild would be best, but also most expensive, at least
in relation to my poverty debt-ridden state, unless you know someone
who would do it for a few beers or dinner which I can arrange.  (I have
just finished blowing the family budget breaking the bank on putting
together a museum of recorded sound.  Just starting on conservation
issues.)

I am in Maryland.  My machine is a musical casket; I think it is called
No. 2.  As one trained in conservation I want to do it right and I know
the issues.  The only thing I have seen recommended was rubber cement
coated with talc.  I know how unstable rubber cement is: it breaks down,
turns brown, cracks.  The heavy duty variety also becomes stiff.

The difference with what seems like a latex-based tire sealer is that,
used minimally, it should be flexible.  Of course, I need to experiment.
If it is a sufficient aerosol (that is, a fine mist) then it will not
block air 100%.  This can also be tested.

Another problem is that it may not work on large openings.  My bellows
does not have these, although there are worn areas on the edges, etc.,
which may open later.  If the material remains flexible, coating these
from the outside where the wear is worst might work.

Where do you get Phenoseal?  I want to look into that as well.

Another question: would there be directions for taking the bellows
apart?  I have taken apart lots of things; I generally can get them
together, but I have learned that I should ask several times and take
apart once.  So...

One would think that it is not too difficult.  I don't want springs
flying through the air, if you know what I mean.  So anyone who can
give me a simple list of steps, it would be greatly appreciated.

Once I remove the old fabric I will have to obtain fabric and I shall
need a source and then I have to cut it to shape and attach it.
Templates would be most helpful if any exist.

So lots of questions, but I am in the early stages and need to take
my time and get things organized and right.

Thanks again for your responses.  Thanks in advance for your time and
assistance.  I hope to get this one machine back to excellent health.

Conrad Bladey