martenot-style string synth

[choklitlove]

i don't really know what i'm asking. i'd really like to figure out the secrets of the martenot. i googled it, and just found some history like these-
http://www.peterpringle.com/ondes.html
http://csunix1.lvc.edu/~snyder/em/mart.html



then i searched the forums here and found this- http://electro-music.com/forum/viewtopic.php?highlight=martenot&t=7710
which is getting closer to what i want to know. but it seems that thread is very old and no one wants to talk in it anymore.


basically, i'm just interested how it uses a string of some sort to move side-to -side to change pitch, create vibrato, portamento, etc.

any more info on the inner-workings?

[Uncle Krunkus]

The idea is similar to the way old radios moved a needle up and down a graph of frequencies. At the same time a variable cap of some sort was being turned, and it was driven by someone's thumb on a wheel. A piece of string (with a tension spring in line) joined them all together. Now if you replace the cap with a variable resistor and drive that by moving the string in a linear fashion, that's a martenot.
The picture you posted is almost right (I remember seeing this picture somewhere before), but the string needs to be in a continous loop, ie: - it returns to the other bobbin on the other side. Like this: -
______
(o)_____(o)

It goes around each bobbin say 2 or 3 times. The tension spring stops it from going slack. Under each bobbin I would put a pot. How you wire them is up to you.
The trick is to take this basic mechanism and refine it so that you get the maximum linear travel, and a certain amount of accuracy which will make it more "playable".
Hope this helps.
Andrew