They are not digital computers.  On the other hand, it would have been
possible to build computers out of a combination of player-piano and
electric-theatre-organ technology during the 1920's.

I haven't checked Babbage's plans carefully, but I believe that his
gear angles could have been converted into bellows and relays.
Articles in New Scientist about seven years ago mentioned the recent
construction (at the British Museum?) of a working portion of a Babbage
machine, the Analytical Engine, I believe.  Separately, someone has
built the Analytical Engine in software and executed upon it a program
written by Lady Lovelace.  Sorry, I don't have the references.

If an electro-pneumatic computer had been built in the twenties, we
would have had a twenty-year head start in computational theory.  I
wonder if the Year 2000 problem would have been resolved by 1977?  Or
would all that legacy electro-pneumatic hardware have given us other
problems instead?

Peter Neilson
Sanford NC