-(The above drawbar setting is often notated: *84 8000 003*.)
+(The above drawbar setting is often notated: *84 8000 003*, an example of DrawbarRegistrations
.)
The footages stamped into late model drawbars refers to the relative lengths of pipes used in a pipe organ. The number of feet refers to the approximate length of the pipe that sounds when the lowest key is pressed on the keyboard. The low C key on an organ normally sounds a note of approximately 65Hz. A pipe approximately 8 feet long is required to sound at this frequency. A longer pipe sounds lower and a shorter pipe sounds higher. To halve the frequency and sound a note one octave lower, a pipe needs to be twice as long. Thus, a 16' pipe sounds one octave lower than an 8' pipe and a 4' pipe sounds one octave higher. Fractions are used when the harmonics are not on octaves of the fundamental. 2 2/3', for example, is the third harmonic of 8' and it is an octave and a fifth above.
It might seem odd that the 5 1/3' drawbar was included, especially since it is positioned to the left of the 8' drawbar instead of the right. This is the third harmonic of the 16' drawbar and with the 8' drawbar (the second harmonic) provides a little tonal color to the 16' drawbar. It might seem odd, too, that the 7th harmonic is missing (which see below), but that overtone would sound distinctly out of tune from a Hammond ToneGenerator.
-On H-series and X-series organs, there are two additional black drawbars appearing to the right of the 1'. The first controls 1 1/7' and 8/9', the 7th and 9th harmonics; the second controls 4/5' and 2/3', the 10th and 12th harmonics. Again note that the first of these includes a pitch which is also out of strict sequence order on the drawbar layout, and that the 11th harmonic (likewise 13th) is missing due to tuning issues.
+On H-series and X-series organs, there are two additional black drawbars appearing to the right of the 1', extending the HarmonicSeries
. The first controls 1 1/7' and 8/9', the 7th and 9th harmonics; the second controls 4/5' and 2/3', the 10th and 12th harmonics. Again note that the first of these includes a pitch which is also out of strict sequence order on the drawbar layout, and that the 11th harmonic (likewise 13th) is missing due to tuning issues.
+
+ <?plugin OldStyleTable
+ |^ *No.* |^ *Harmonic*|^ *Interval* |^ *Footage* |^ *Color*
+ |^ 10 |7th Harmonic <br> 9th Harmonic |Flat Twenty-First <br> Twenty-Third |^ 1 1/7' <br>8/9' | Black
+ |^ 11 |10th Harmonic <br> 12th Harmonic |Twenty-Fourth <br> Twenty-Sixth |^ 4/5' <br> 2/3' | Black
+ ?>
On the bar which connects the tab to the switch inside the organ are marked numbers 1 through 8 (when the drawbar is pushed fully into the console, the drawbar setting is considered 0 and no harmonic will be heard). As the drawbar is pulled towards the player, each number represents roughly a 3dB increase in the volume of the harmonic that drawbar controls. Pulling it out by two increments gives a doubling of the volume of that harmonic. Conversely, as the drawbar is pushed in, each number represents a -3dB change in the volume of that harmonic. Pushing it in by two increments gives a halving of the volume of that harmonic.
In most Hammonds, each manual key has nine contacts which which close more or less simultaneously when the key is depressed. Each contact is wired to one of the 91 [ToneWheel]s in the ToneGenerator. The [ToneWheel]s selected for the contacts in each key represents a harmonic series of sine waves for that key. Each contact connects the nine [ToneWheel]s for that key's assigned harmonics to nine [BusBar]s which run the length of the manuals. Each busbar is connected to the sliding contact on one of nine drawbars. Each drawbar can be moved to connect the tones on that busbar to one of nine fixed contacts. Each fixed contact is connected to one of nine primary windings on the MatchingTransformer. The matching transformer is wound so that as each drawbar is pulled out, the busbar is connected to a winding that is half the impedance of the drawbar position beneath it.
