These are wonderful and thanks for posting the link.  I find myself wondering how these work from a mechanical viewpoint, but give up when I realise that this particular instrument is reminiscent of the swan - serene and graceful above the water - paddling like mad underneath.

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All the Woes of a World by Jonathan Icknield aka The Bryster

And in my final hours - I would cling rather to the tattooed hand of kindness - than the unblemished hand of hate...