A few weeks ago Moe Goldy posted asking about the simple whistles found
in the tweeting bird bocages where the birdsong is produced straight
from the bellows [111030 MMDigest].  The bellows contracts expelling
air through a metal disc and then sucking in again as it expands to
produce a lower note.

The metal discs are actually two discs with a space between; the ones
I find loud and effective are made for a repro tin toy called the
Whistling Partridge which works on exactly the same principle.  The toy
is currently available from http://www.tintoyarcade.com/ in the USA for
about $6.  The pill-shaped whistle clips out and is easy to fit over
the bellows hole on the bocage mechanism.

To enhance the realism of the tweeting flock, Lyn Wright in an old
MBSGB journal advised varying the lift on the bellows to produce a
changing length of note.  The pinned cam that turns to lift the bellows
lever can have the pins at varying distances to help achieve this.

Tweet Tweet!
Michael Start - The House of Automata
Scotland

 [ See http://www.tintoyarcade.com/search.php?search_query=Whistling 
 [ "Partridge Whistling Flapping Tin Toy"  -- Robbie