The drawbars on the Continental organ are used for voicing and tone control and are based on the operation of a pipe organ.
The concept of drawbars for voicing control was originally developed by Hammond Organ in the 1940s. Hammond organs used 9 drawbars that controlled the volume of nine different electronically simulated organ pipe lengths. From left to right, these drawbars were connected to tone generators inside the organ that operated the simulated pipe lengths of 16', 5 1/3', 8', 4', 2 2/3', 2',1 3/5', 1 1/3' and 1'
The Vox Continental drawbar system borrowed heavily from Hammond. On the Continental, the left four drawbars are labeled 16', 8', 4' and IV. As on a Hammond organ, these voicing drawbars act as volume controls for the electronically simulated pipe organ lengths they control. The Vox Continental drawbars are connected to the output of the serial dividers on the tone generator cards through the key contacts.
The sixth divider on the tone generator cards produce the lowest tones on the organ (click here for an explanation of the divider operation on the V301E tone generator cards) . The output of the sixth, ot lowest divider on the tone generator card is roughly equivalent to the tone produced by a 16' pipe on a traditional pipe organ. In the lowest octave of the organ, the 16' drawbar is connected to the output of the sixth divider, adjusting its volume. The drawbar may be pulled out to make the tone louder and pushed in to make the tone softer. Again, in the lowest octave, the fifth divider on the tone generator card feeds the 8' drawbar, making a tone equivalent to an 8' pipe on a pipe organ and produces a tone one octave higher than the sixth divider. The same applies to the fourth divider and the 4' drawbar, which produces a tone two octaves higher than the sixth divider.
In the second octave, the 16' drawbar is connected to the fifth divider on the tone generator card. In the third octave, the 16' drawbar is connected to the fourth divider on the tone generator card. In the highest octave, the 16' drawbar will be connected to the third divider of the tone generator card. The similar scheme would apply to the connection of the 8' and 4' drawbars to the tone generator cards.
The drawbar labeled "IV" is called "the fourth rank." The fourth rank is a combination of four tones, again based on the length of the pipes on a pipe organ that would produce these tones. The tones are based on the 2 2/3' , 2', 1 3/5', and 1' pipes. These are considered to be "overtones," and make the tone of the Continental more complex when compared to the Vox Jaguar organ, which does not offer this tonal option. The choice of these four overtones (2 2/3' , 2', 1 3/5', and 1') for the Continental was obviously influenced by the circuits of a Hammond organ, which offered these same four semitones on four individual drawbars.