Drawbars

are the main method of controlling the sound of a Hammond tonewheel organ or a clonewheel. Not all drawbar organs have the characteristic tonewheel sound and not all tonewheel (or clonewheel) instruments have drawbars.

A drawbar is essentially a volume control - it controls the level of one of the footages of the organ's sound (on some non-Hammond instruments, notably the 1960s Vox Continental, drawbars have also been used to determine the level of different organ tones - e.g. flute and reed).

It normally takes the form of a narrow horizontally-mounted metal bar, marked with gradations from 1 (near the player) to 8 (away from the player) and with a small knob or handle at the near end. Early drawbars had a ratchet mechanism which meant they could only be drawn in whole increments; more recent ones have had a smooth, continuous action.

An archetypal Hammond has two sets of nine drawbars per keyboard. They follow the layout illustrated below:

The 5 1/3' is placed between the 16' and 8' because its aural function is to reinforce the bass; this is an auditory phenomenon known as resultant bass or acoustic bass.

There are also normally two drawbars (16' and 8') for the pedalboard.

Although a Hammond-type organ can only produce sine waves, its drawbars enable the player to adjust harmonics so as to produce a huge range of tones.