Flex-a-tone is the sort of sound I am after. So, in the same family of sounds, I looked into the musical saw. I made a rough bow and tried to play one carpenter saw that was around and could not make much of it before I read this tutorial. 

So, everything is in the S shape. Wow. Such a nice sound. That said, the physic of if is streakily not straight forward. I don't seam to be able to reproduce on other pieces of metal I have around, that have more of a rectangular shape, maybe it is that.

And you know what, a flex-a-tone as a S shape too.

Révélation du jour....