If its flute related, I had a bit of experience when working on The Warriors Way of needing the sound of the last air exiting a neck wound after someone was killed by a Samurai - the script referred to it as a 'sad flute' I experimented with a lot of ideas but got the best results by hiring a local guy who is a genius with all sorts of wind instruments. He has a massive collection from many different culture but also is very skilled at various playing techniques (overblowing to create harmonics etc) http://en.wikipedia.org/wiki/Overblowing

Myself and the director got him to try all sorts of musical & non-musical/atonal phrases that I then messed with.. For my use I also filled a few ocarina and bamboo flutes with water and yoghurt, and captured elements to simulate lungs filling with blood etc...

fun!

I'm pretty sure it'd just have been sound designed. I don't think there would be time and budget to spend on designing functioning props like that; it would essentially be like designing a musical instrument specifically for use in a couple of scenes!

The design of the sound would probably have involved the use of some flute sounds, the lower parts from blowing across something like a drainpipe.

Old Disney cartoons used a lot of purpose built machines for sound effects, but that is as far as I know very rare now.

I can't say for sure what it originally was that made that sound, but it wasn't from the prop. Like Tim mentioned, it might very well be some kind of flute, very possibly a Chinese or Japanese flute played by someone truly brilliant. My guess is the Shakuhachi.

It does sound very bamboo:ey.