Thank you Robbie and Don for your answering my question on "bird
whistle", singing "bird pipe".  What I am looking for are the design
parameters for (what I would prefer to call) a pipe -- a pipe that
could be tuned interactively by a moving piston, as it is in the
well-known singing bird cages or snuff boxes.

The "birdsong" in a baroque organ, produced by "organ pipes plunged
headlong into a water vessel" will not allow the bird to sing a melody,
it can just "twitter".

I am wondering if really nobody did some systematic investigation of
"bird pipes" and published the results.  So I think I have to start
with some basic experiments by my own.

If ever I will succeed with the design and later on with the technical
implementation of my "automaton idea", I will report about it.

Regards from Germany,
Christian Greinacher

 [ The Popper "Roland" orchestrion featured a slide whistle as you
 [ describe; Popper called it a "Swanee Whistle".  The position of the
 [ sliding piston is calibrated for each note, which assures better
 [ pitch intonation than can be achieved by most human musicians!
 [ See & hear it playing at http://www.youtube.com/watch?v=_P9dMlNH5jU 
 [
 [ A similar orchestrion by Paul Lösche Orchestrionwerke employs
 [ a ported follower valve to properly position the slide.  It is
 [ is described at http://www.mmdigest.com/Pictures/loesche1.html 
 [ -- Editor (Robbie)