Hi Brent et al - This subject has been discussed on our Clarinet Bulletin  
Board  _www.woodwind.org_ (http://www.woodwind.org)  several times  and if you 
use its Search function for the above words you may find the  info for which 
you are asking.  Probably Wikipedia will also have a  paragraph or two about 
this old/still-current technology.  Luck ,  Don



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