Nord User Forum

I have noticed that some parts of keyboard (NE5D-61) seem to generate slightly different versions of the sound played from other parts of the keyboard (apart from pitch). Using a B3 voice I found that several keys in the C2 octave (Eb2 - Gb2) did not respond to my drawing the 1 3/5, 1/1/3, 1 bars whereas their effect was clear in other parts of the keyboard both above and below the keys in question. Not a velocity issue I think but could it be a keyboard fault or is it inherent in the inbuilt organ voices? The same kind of difference is also noticeable for other sounds but not necessarily affecting the same keys on the keyboard so whatever it is does not seem to be key-specific.

OS up to date and factory sounds recently reinstalled

"Hammond ConsoleOrgans have 61 keys on each manual. The number of ToneWheels necessary to produce all 9 harmonics for all 61 keys is 109. Since all console models have either 82 or 91 frequency generators, certain outputs are reused for the upper harmonics of the keys at the upper end of the manual. This characteristic of repeating, for the harmonics of an upper octave, the harmonics used for a lower octave is called foldback."

http://www.dairiki.org/HammondWiki/HarmonicFoldback

Try this to understand how foldback works:

Turn off the C/V, percussion, EQ and the rotary simulator. Pull out only one drawbar. Play chromatically up or down the keyboard, and listen to where the octave of the drawbar "resets" by jumping up or down one octave. That is the point where the drawbar is folding back.

Repeat for each drawbar. Once you've done that do the same experiment, only using two drawbars. You will hear the difference in their relationship as you move up or down the keyboard.

It is this foldback relationship between the notes that affects why some notes sound "stronger" and others "weaker".

In some models of the Hammond (such as the M3), the foldback is less than fully implemented. That is, the 1st drawbar does not fold back beyond a certain key. It's part of what creates the timbral variation between the models.

Thank you so much for this excellent explanation. Fascinating and now understood

Also note that on the spinet models (like the L-100 series), rather than implement foldback on the lower registers, they just eliminated the bottom two drawbars from the lower manual altogether.