G'day Kevin et al.
Two ideas that do have merit. One the Helmholtz resonator, the other the chime whistle.
At beer o'clock in an office yesterday I finished my stubby of beer and was walking with it back to the kitchen. As I did so I was swinging my arms and became aware of the low note produced as the wind passed over the lip of the bottle. Try blowing over the lip of a soft drink bottle if you are not a beer drinker.
A stubby bottle produces a low note, guess two octaves below middle C corresponding to stopped whistle about 1.2 metres long, and yet the stubby is only 200mm long with volume of 375ml.
Solution: drink a stubby bottle of beer (and a few more just in case the bottle breaks, you need spares ;D ). Attach bottle to loco and then blow steam across the lip.
The chime whistle is a concept that the English readers may not know. A chime whistle comprises a bell divided into about 5 chambers by axial dividers, each chamber is a separate length. The annular steam jet is much the same as for a bell whistle and blows across the lip of each chamber. Because the chambers are different lengths the notes produced are different. The resulting sound is a chord (dischord) which you hear due to acoustic interference as a much lower note.
Making a chime whistle seems like too much work, I like the stubby idea better!
OGTDA
Regards,
Ian