[BC] Mutual Tones?

[charles hobbs]

I remember them sounding something like this:
http://www.lerctr.org/~transit/projects/mt.mp3

Note: This was just me fooling around with Goldwave, and making it sound sort of like how I remembered them. (Yes, I am being deliberately vague).

I have no idea of the actual frequencies used, so don't take this as canonical!

Also, there's a nasty click on the end sometimes....

But let me know what you think.