[sdiy] Number of tonewheels in a drawbar organ

[Tim Ressel]

Steve,

>From http://www.electricdruid.net/index.php?page=info.hammond:

	* 12 tonewheels of 2 teeth
	* 12 tonewheels of 4 teeth
	* 12 tonewheels of 8 teeth
	* 12 tonewheels of 16 teeth
	* 12 tonewheels of 32 teeth
	* 12 tonewheels of 64 teeth
	* 12 tonewheels of 128 teeth
	* 7 tonewheels of 192 teethFor a total of 91.

--TimR




----- Original Message ----
From: Steve <steve.moorby at ntlworld.com>
To: synth-diy at dropmix.xs4all.nl
Sent: Mon, May 31, 2010 9:25:15 PM
Subject: [sdiy] Number of tonewheels in a drawbar organ

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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