Characteristics of the Hammond Organ - Saels Family

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Characteristics of the Hammond Organ

Hammond Organ
The Hammond tone wheel organ was introduced by Laurens Hammond in April 1935. His method for producing sound was new. The sound had a special character, very warm. Therefore a lot of people loves the sound of a Hammond organ.

The current new manufactored Hammond organs can produce the sound of the early Hammond organs, such as the wellknown B3, thanks to the new electronic sound approach.

Here-after some characteristics of the old Hammond organ is explained, because all new organs are trying to copy the features of the old ones.

A Hammond console organ includes two 61-key manuals; the lower, or Great, and upper, or Swell, and a pedal board consisting of 25 keys. The concert models have a 32-key pedalboard.

The spinet organ has a pedalboard of 13 keys (1 octove). Mostly the organ will have less keys, e.g. 44 to 49 keys for the upper and 44 to 49 keys for the lower manual.

1. Drawbars

The secret of the Hammond tone wheel organ lies in its method of tone production. The tone generator assembly consists of an AC synchronous motor connected to a geartrain which drives a series of tone wheels, each of which rotates adjacent to a magnet and coil assembly. The number of bumps on each wheel in combination with the rotational speed determines the pitch produced by a particular tone wheel assembly. The pitches approximate even-tempered tuning, (it's done with integer math after all).

A note on the organ consists of the fundamental and a number of harmonics, or multiples of that frequency. In the Hammond organ, the fundamental and up to eight harmonics are available and are controlled by means of drawbars and preset keys or buttons. The setting at any particular time is applicable to one manual, either Great or Swell. (Harmonic content adjustment is provided for each manual independently.) The Hammond organ creates its tone colors through additive synthesis.

Mostly the Hammond organ has 2 sets of nine drawbars (one for the upper manual and one for the lower manual) and 1 or 2 drawbars for the the pedalboard. Some of the better organs have even more drawbars, e.g. the B3 has 2 sets of 9 drawbars for each manual / the H100 has 2 sets of 11 drawbars for the upper, 2 sets of 10 for the lower and 4 drawbars for the pedalboard.

Each drawbar is marked with a number followed by a footage mark. For example, the first white drawbar is marked 8". This is pipe organ terminology indicating that the pipe used to produce the lowest note on the keyboard on a pipe organ is actually eight feet long. The numbers from 1 to 8 on each drawbar represent degrees of loudness (number 1 is the softest, and number 8 is the loudest).

Next table illustrates the relation of the drawbars to the manual when the middle "C" is pressed.

Pipe Pitch16'5 1/3'8'4'2 2/3'2'1 3/5'1 1/3'1'
Scale Interval
C - 1 octave
G note
Middle C note
C + 1 note
G + 1 octave
C + 2 octaves
E + 2 octaves
G + 2 octaves
C + 3 octaves
Stop Name
Bourdon
Quint
Principal
Octave
Hazard
Block Flote
Tierce
Larigot
Sifflote

The combination of the used drawbars give some very nice sounds. Some of the nice drawbar registrations are indicated somewhere else on this website.

2. Percussion

Hammond Percussion is the name that Hammond gave to a patented circuit that changed the attack characteristic of a note. It does this by adding an additional tone, the Percussion signal, to the note that is depressed. The envelope of the Percussion signal is controlled to have a specific decay characteristic. The frequency of the Percussion signal is selectable to be either the 2nd or 3rd harmonic of the depressed note. The audible effect of this is that there is a chirp or ping at the attack of the note.

In modern keyboard parlance the Hammond Percussion would be called "single triggered". The Percussion envelope amplifier is triggered only when a note is depressed from an all-keys-up state. After it has been triggered and as long as any upper manual keys remain depressed, no Percussion effect will be heard when additional notes are depressed. Thus to hear the percussion effect for every note of a run requires a technique that fully releases the currently pressed key prior to depressing the next one in the run.

When Percussion is enabled, one of the harmonic busbar contacts from each key is used to trigger the Percussion amplifier. This removes one drawbar harmonic from the palette available to shape the sound.
Second Harmonic

The tone for this harmonic is the same as the sound derived from the 4' drawbar. Combining the 2nd harmonic to the drawbar will produce bright and clear sounds.
Third Harmonic

This harmonic tone is the same one produced by the 2 2/3' drawbar. Combining this 3rd harmonic to the drawbars will produce powerful and heavy sounds.

On the console organs equipped with percussion, it is enabled only on the upper manual.

3. Key Click

The sound produced by early Hammond organs differed from pipe organs in one characteristic way. There was an attack transient that sounded like a click or pop when a key was pressed. This was considered a defect. Considerable design efforts were made to reduce it but it could never be eliminated. Later rock and blues players found the key click characteristic to be desirable and some jazz organists consider it to be essential. Many Hammond organ simulators include a key click control to reproduce this characteristic.

4. Vibrato & Chorus

Provided on the organs so equipped are vibrato and chorus settings V1,V2,V3 and C1,C2,C3.

Vibrato is the periodic raising and lowering of the pitch, and is thus fundamentally different from tremolo which is a variation in only the loudness of the pitch.

V1 = Small Vibrato : This produces the vibrato equivalent of most orchestral solo instruments.

V2 = Wide Vibrato : This is the standard depth vibrato to produce the effect of a theater organ.

V3 = Full Vibrato : This gives the fullest amount of vibrato, adding much warmth and enhancing your music.

The chorus signal is produced by adding non-pitch-shifted signal to the pitch-shifted signal.

C1 = Small Chorus : This produces the light chorus effect.

C2 = Wide Chorus : This is the standard depth of the chorus effect.

C3 = Full Chorus : Now you get the fullest amount of chorus, adding warmth that enhances your drawbar settings.
Website created by Manu Saels
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