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so when I get one that plays nicely, I keep it going until it falls apart. I have tired a bit of scraping, but usually make things worse
Once the reed has lost its elasticity, springness...whatever you call it... then nothing can save it.
The scraping, sanding, balancing etc has to be done to prepare the reed at the beginning.
The reed is/was a living thing. Its elasticity is due the millions of long lignin molecules all linked.
As you play it, they get broken.
Like a bow and arrow.
You can stretch a long piece of wood just so many times till it finally becomes weaker.
If it were not the case, our museums would be full of bows from Robin Hood, Agincourt etc!
But they're full of dinosaurs etc!
Oh... and bored schoolteachers with their classes!
Steve