There were theatre (cinema) organs built with singing bird pipes in
chromatic order.  The Regal Marble Arch organ [London] comes to mind.
I have made two of these sets of tuned bird whistles many years ago.

The compass is usually no more than 18 notes.  The pipes are not like
most organ flue pipes which have the windsheet (air reed jet) impinging
on the outer part of the upper lip of the pipe.  Since the open end
of the pipe resonator is immersed into an oil trough, so the pipe will
"chirp" when played, the windsheet must be focused on the inside of the
pipe to build up pressure that will drive down the liquid for the chirp.

Each pipe is movable up and down into the liquid for tuning.  Thus each
pipe is winded via a rubber tube to the chest action.  The pipes will
be blown on fairly high wind pressure so that the resonator pressure
will be sufficient to drive down the oil.  They also work better when
immersed into the oil at an angle so less pressure is needed to move
the liquid for the chirp.

Virtually every Wurlitzer theatre organ had at least one "bird whistle"
which was a small whistle played from a key cheek button or toe piston
so the bird chirping in the silent movie would have a voice.  They were
normally filled with water which evaporated, light oil, or glycerin.
These metal types can still be found in many large music stores and
some on line catalogues.  The plastic toy bird whistles were available
at Toys-R-Us only a few years ago.  From these one can see the whistle
section is a simple cylinder with a mouth that is simply a cut out
section and the languid set to blow the wind straight into the resonator.

I have never worked on a mechanical chirping bird music box, but
I assume it would have dry pipes with stoppers that would be lifted
away rhythmically to produce chirp.

I hope this helps.

Kindest regards to all on MMD,
Al Sefl

 [ At http://www.theatreorgans.com/southerncross/Radiogram/UKfiles.htm 
 [
 [ "The Marble Arch Christie was the largest unit theatre organ built
 [ outside the USA.  Its many unusual features included two octaves of
 [ tuned bird whistles -- these can be heard in some of the recordings.
 [ As far as is known, Christie built three sets of these bird whistles,
 [ the others being at the Regal, Edmonton and Regent, Poole.  In the USA,
 [ a few Robert Morton organs had a similar effect, called 'Canaries'".
 [
 [ The bird whistles are featured in audio recordings on this web page.
 [ -- Editor (Robbie)