Several years ago I got into making pennywhistles out of pvc. My main goal was to get a low whistle without paying hundreds of dollars, but once I figured out the basic principles it was a lot of fun experimenting. I found one of those experiments yesterday and got it out:

That's a 5' overtone flute in A. It's six times the length of a standard D whistle, so the lowest note it can play is two and a half octaves lower, at 110 Hz. The flute is very narrow for its length, though, so it's extremely quiet playing that note and instead is much more at ease when playing overtones.

The available notes are all multiples of the base frequency:

note	frequency
110 Hz	A
220 Hz	A
330 Hz	E
440 Hz	A
550 Hz	C#
660 Hz	E
770 Hz	G
880 Hz	A
990 Hz	B

I'm not very good at playing it, but it sounds like this: mp3.