[CAUT] Tuning the back duplex

[Richard Brekne]

Hi folks.

I have been spending a lot of time lately playing with various ideas in 
relation to the back duplex length.  I know there is a lot of back and 
forth discussion about the viability of this idea... but the following 
thoughts have prompted me to start looking closer at this whole thing.

It has been stated time and time again here that the friction levels 
needed to be overcome for a change in tension to occur for this length 
are great enough that if true, one can assume that this length would 
remain quite stable during play, perhaps more so by a good deal then the 
speaking length. This would mean that any (reasonable) pitch adjustment 
to  of these lengths could easily be done during the course of a usual 
tuning. I find routinely that the pitch of these lengths for unisons 
vary quite a bit and these variant pitches remain stable from tuning to 
tuning. This allows for quite a large window for which to tune these 
lengths to.

It strikes me as intuitively obvious that lengths of the same length 
should have as identical pitches as possible. In fact, it is quite easy 
to accomplish this with an ETD on the fly as a part of a regular tuning. 
If you need to increase tension, just use a string hook and pull on the 
speaking length close to the bridge pin in a direction away from the 
pin.... or simply tune the string quite high until the back length rises 
in tension enough.  To go the other way simply do the same on the duplex 
length. Fine adjustment is easier then you might think. In fact the 
whole process doesnt add all that much time to a regular tuning, and can 
be expected to hold pretty darn solidly at least as long as the next 
seasonal change. Climatic changes affect the whole darned instrument so 
this is not a reason IMHO to not tune this section.

Now... just what is the most optimal frequency relationship to the 
speaking length to tune these lengths too is another question.  I'm 
getting the feeling that if one assures that the tension is higher in 
the back length then the speaking length.... that you end up with a 
cleaner sounding instrument.... but I am still experimenting.  Any 
thoughts would be greatly appreciated

Cheers
RicB