Cracking the unisons

[Andrew and Rebeca Anderson]

Greg,
I do this when my tuner indicates that the total 
unison ended up flat, usually less than two 
cents.  Much more than that and I need to break out the mutes.

Andrew Anderson

At 12:13 AM 1/6/2006, you wrote:
>I'm hoping someone will take a stab at a detailed
>definition of "Cracking The Unisons".
>
>I've checked the archives, and lots of people mention
>Virgil Smith's technique, some claim to use it, only a
>few have partially described it, and I suspect I'm
>still not getting it.
>
>As I understand it:  If a three-string unison is found
>to be slightly flat or sharp compared to a test
>interval or two, you adjust the first string without
>muting the other two, then adjust the remaining
>strings to clean up the unison.
>
>Reasons for doing this:  It's faster than messing with
>mutes, it produces better unisons, it avoids the
>"Virgil Smith Phenomenon" of a unison going flat when
>all three strings are vibrating compared to a single
>string of the unison by itself.  (Please, let's not
>debate the phenomenon.  I'm just asking about
>cracking.)
>
>Is this all there is to the technique?  I presume the
>hard part is being able to hear the beat clear up on
>the 2nd string while the 3rd is still beating away,
>akin to dealing with false beats.
>
>Some of the unanswered questions (in my mind):
>
>1.  How big an adjustment to the unison are we making
>when using the cracking technique?  One BPS? Half a
>beat? One beat in 15 seconds?
>
>2.  Do we move the 1st string to create a beat rate
>matching the out-of-tuneness of the unacceptable test
>interval, or is there some other method at work?  If
>the 5th is beating about 1/2 BPS too fast, do we
>create a 1/2 BPS unison, then move the other two
>strings to eliminate the beat?
>
>3.  The single vs. three string pitch change "Virgil
>Smith Phenomenon": How big a change are we talking
>about?  I've read 0.1 to 0.3 cents.
>
>How close is "close enough"?  I know I'm not yet good
>enough to hear some of these small errors in unison
>tuning.  I don't know if I could tune two strings to
>0.25 cents accuracy while the third was 1.0 cent out.
>Heck, who am I kidding?  Sometimes I don't hear the 1
>cent error, especially in upper octaves.  0.25 cents
>mid keyboard is about one beat in 16 seconds, right?
>Is that the kind of accuracy we are talking about
>here?
>
>I need to see and hear this demonstrated someday, but
>I'm hoping someone on the list who is a "crack addict"
>can help me with a better written description.  The
>archives need clarification, as do my unisons.
>
>Thanks,
>
>Greg Graham
>Brodheadsville, PA
>One tuning exam (and several months) away from
>RPT-dom.
>
>
>
>
>
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