string coupling effect

[Richard Brekne]

Hi list.

Today I was dinking around with my handy dandy newly fixed laptop and
tunelab... getting ready to finnally get started taking all those
measurements I have been wanting to get started on. I was fooling around
with ways of useing tunelab and thought I'd relate an odd observance I
had under the process.

First... let me say this was a Sweedish Nordiska from about 20 years
ago. Second... from my temperament octave a3 - a4 I set Tunelab to read
the 4th partial of each progressive note up from a4 and kept this for a
whole octave. I used this 4th partial to tune the next two octaves up
for each note between a4 and a5. This, in other words gave me a 4:2:1
relationship for each triple octave (a4 to a5) Just wanted to see what
this sounded like dont you know... grin.

What I noticed was this.. On the highest note of each triple octave the
string coupling effect was like reversed ???? Also... the frequencies
got higher as I coupled in the unison strings.  At first I thought this
must be the pins fooling me and rising a bit.. but after checking and
rechecking I could not deny that playing a single string gave a lower
frequency reading then playing two or three in each unision. This varied
a bit in amount from note to note... but never did I see what we usually
see.. ie the opposite effect.  More baffeling to me was the fact that
after further fooling around with this I noticed that if I tuned the
unison (again.. the highest unison of each triple octave from a4 to a5)
just a bit flat of the 4:2:1 relationship... ie 4:2:-1, then things
reverted to  "normal". That is to say, tuning the highest note just a
bit flat of  4:1 ,, 2:1  led to the unisons going flat as each string
was coupled in.

Anybody got any bright eyed explanations for this ??.. I will repeat
this process next week to see if it was just a weird fluke, some
headache I hadnt registered.. or whatever. But in the meantime I am
interested in anyones thoughts on the experience.

thanks...

--
Richard Brekne
Associate PTG, N.P.T.F.
Bergen, Norway