[sdiy] Number of tonewheels in a drawbar organ
Steve
steve.moorby at ntlworld.com
Tue Jun 1 06:25:15 CEST 2010
Hi all,
How do you calculate the number of tonewheels needed by a drawbar organ?
I've seen various figures such as 91 and 96 but these seem lower than my
calculations.
My logic (for a 5 octave, 61 note keyboard) goes as follows :-
* Start by considering fundamentals 8' for 5 octaves, 60 notes C -
B gives 60 tonewheels.
* Considering the 4', 2' and 1' drawbars extends the 5 octaves by
another 3 to 96 tonewheels.
* The 5 1/3', 2 2/3', 1 3/5' and 1 1/3' drawbars don't add any
more tonewheels, their frequencies are already present.
* The 16' drawbar adds another octave below for the sub-octaves of
the lowest octave on the keyboard giving 108 tonewheels.
* The top C of the keyboard requires just one more tonewheel for
the 1' drawbar.
This gives a total of 109 tonewheels for a 5 octave keyboard. Even more
would be needed for two manuals and pedals.
I've checked my logic above with a program that just lists all the
frequencies by looping through each of the drawbars for each of the
notes.
So what am I missing?
Thanks
Steve
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