From bruce@ashbysolutions.com Sun Nov 20 15:03:25 2005
Subject:Re: Real tone wheels

Hi Lou,

There are lots of online resources, including the Hammond-Leslie FAQ (http://theatreorgans.com/hammond/faq/), the Hammond Wikipedia (http://en.wikipedia.org/wiki/Hammond_organ), and HammondWiki (http://www.dairiki.org/HammondWiki/).

Some quick off-the-cuff answers to your questions:

>I know it is a rotating wheel (metal I guess) that has a magnetic coil pickup. Does anybody have any good photos of a real tone wheel? I don't think I have ever seen one. I have seen some pages where there are hand-drawn pictures. Is there a separate tone wheel for each note on the keyboard?

There is a separate tonewheel for each drawbar tone on the organ, but not enough to cover 61 keys x 9 pitches, even with duplication. There are 91 tonewheels in a B-3, while other models have 82 (?) or 96 tonewheels. The console models (B-3, C-3, A-100, etc.) use "foldback" -- re-using of the same pitches an octave higher or lower -- to fill in the gaps; most of the spinet models just leave the missing tones out.

>Secondly, I can see how a tone is generated using a spinning wheel, but I do not see where the drawbars come into effect with the tone wheels. I know they change the sound, but how is that done?

The work like faders on a mixing board, adding in different levels of harmonically-related tones. Essentially, a Hammond Organ is an additive synthesizer, taking (near) sine waves and combining them to make more complex tones.

>Why are the drawbars labeled after pipe organ tube lengths?

The standard convention in pipe organs is to label a register with the length of the lowest (?) C pipe, and since Laurens Hammond designed the organ as a pipe organ replacement for churches, he designed the drawbars around familiar terminology.

>I have downloaded some schematics on the Hammond B-3 and have looked at them a little. It might be nice to have a tutorial to go along with them :-)

There is plenty of technical information in the three sources I mentioned.

Regards,

-BW

--
Bruce Wahler
Design Consultant
Ashby Solutions™ http://consult.ashbysolutions.com
978.386.7389 voice/fax
bruce@ashbysolutions.com

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