In essence, the Hammond drawbars can be thought of as an upside-down graphic equaliser, and that's exactly how imaginative players use them to create their individual tones. You still have the bass on the left and the treble on the right, but because the bars are pulled out (or pulled down on a virtual instrument) to increase their effect, the ‘EQ curves’ appear vertically flipped. Provided you’ve used a graphic equaliser, you should be able to relate to the Hammond drawbars straight away.
You can get involved in all sorts of discussion about pipe lengths, fundamentals, octaves and what have you, but broadly, the Hammond drawbars can be considered a set of nine tone controls, ranging from deep bass on the left to sparkling treble on the right.
I’m going to begin by assuming you haven’t used a graphic equaliser, and start with a much simpler view of the system. Let’s pretend the Hammond has just three drawbars: a bass, a middle, and treble control – just like a basic hi-fi, but in the form of pull-out bars rather than rotary knobs. In the diagram below I’ve shown this three-bar Bass/Middle/Treble system as it translates to Hammond drawbars. On the left, a bassy sound is gained by pulling out (or down) the Bass bar to the maximum amount, and setting the middle and treble bars at much lower levels. On the right, the level of the Bass bar is much reduced, while the Treble bar is set to maximum for a trebly sound.
If that makes sense, you now understand exactly how the Hammond drawbars work. All you need do now is add extra frequency stages so that the level of control becomes much more extensive. The diagram below shows the expanded version, as used on a real Hammond, but with the 'footage' markings replaced by three zones. Bass on the left, Middle in the middle, and Treble on the right. As with a graphic equaliser, adding more frequencies from the Bass (left) side of the range whilst keeping the Treble components at reduced level creates a bassy sound. Adding more frequencies from the Treble (right) side whilst reducing the Bass region gives a trebly sound.
Try to think of the drawbars as a unit (a graphic curve or linear representation of the tone) rather than a series of individual components. If you can do that, you’ve got the general idea of how to set your Hammond drawbars for the kind of sound you want. Simply think bass, middle, treble, and pull out bars from the appropriate region of the sound spectrum. For much of the time I ignore the footage readings. This is the intuitive way in which experienced Hammond players have understood and used their instruments. It’s not about saying: “I’m going to set the 4’ drawbar to level 3 and the 8’ to level 7.” It’s about associating the whole set of bars with elements of the frequency range, then visualising, and setting ‘tone curves’. ‘Tone curves’ merely being the visual shapes created by the drawbar arrangements.
Bearing in mind that the drawbar system is vertically flipped in comparison to a graphic equaliser, those who have an affinity with graphic equalisers will recognise the left hand ‘tone curve’ below as giving a ‘scooped’ midrange with strong bass and treble elements. Conversely, the right hand ‘tone curve’ produces a nasal sound, which might in a graphic equaliser be used to simulate ‘speakerphone’ for a human voice. Even though this is an organ, the effect on the timbre is just the same.
True, the Hammond drawbars are physically adding individual pitches to a composite tone rather than merely emphasising or de-emphasising pitches which are already there (as is the case with a graphic EQ). But there's very little difference in the way a given tone curve or line impacts on the tonal character - provided of course that you remember your Hammond drawbar tone curves are upside down. They're vertically mirrored images of your graphic EQ tone curves.
Of course, it’s worth looking into the exact settings some famous Hammond players have used if you want to accurately copy them and learn more about special techniques – like using only the white bars and the 16’ for pure tibia tones, or producing more dissonant tones by mainly using the dark bars. And I should maybe mention that in terms of the frequency bands, the second (5 1/3') and third (8') drawbars along the row are out of sequence. On a graphic EQ they'd be the other way round. But that's not greatly improtant in the grand scheme of this system.
You can of course use your ears to make fine adjustments, but the important thing is that you have a ballpark vision of what's doing what to the sound. The system of imaginary Bass, Middle and Treble zones described in this piece gives you that, allowing you to sculpt your tone in an easy, structured and lucid manner. It’s just like adjusting a hi-fi, so if you're able to adjust your hi-fi to sound exactly as you want, there’s no reason why you can’t do the same with a Hammond.
If you use the VST recording environment, this site offers a good range of freeware organs, some of which use the Hammond drawbar system. They're all available on a fast, no-strings, entirely free download. Please visit the Virtual Organs for Download landing page for full details.
