A number of distinctive Hammond organ features are not usually found on other keyboards like the piano or synthesizer. Some are similar to a pipe organ, but others are unique to the instrument.
Keyboards and pedalboard
The two manuals of the Hammond B-2.
Most Hammond organs have two 61-note (five-octave) keyboards called manuals. As with pipe organ keyboards, the two manuals are arrayed on two levels close to each other. Each is laid out in a similar manner to a piano keyboard, except that pressing a key on a Hammond results in the sound continuously playing until it is released, whereas with a piano, the note's volume decays. No difference in volume occurs regardless of how heavily or lightly the key is pressed (unlike with a piano), so overall volume is controlled by a pedal (also known as a "swell" or "expression" pedal). The keys on each manual have a lightweight action, which allows players to perform rapid passages more easily than on a piano. In contrast to piano and pipe organ keys, Hammond keys have a flat-front profile, commonly referred to as "waterfall" style. Early Hammond console models had sharp edges, but starting with the B-2, these were rounded, as they were cheaper to manufacture. The M series of spinets also had waterfall keys (which has subsequently made them ideal for spares on B-3s and C-3s), but later spinet models had "diving board" style keys which resembled those found on a church organ. Modern Hammond-Suzuki models use waterfall keys.
Hammond console organs come with a wooden pedalboard played with the feet, for bass notes. Most console Hammond pedalboards have 25 notes, with the bottom note a low C and the top note a middle C two octaves higher. Hammond used a 25-note pedalboard because he found that on traditional 32-note pedalboards used in church pipe organs, the top seven notes were seldom used. The Hammond Concert models E, RT, RT-2, RT-3 and D-100 had 32-note American Guild of Organists (AGO) pedalboards going up to the G above middle C as the top note. The RT-2, RT-3 and D-100 also contained a separate solo pedal system that had its own volume control and various other features. Spinet models have 12- or 13-note miniature pedalboards.
The sound on a Hammond is varied using drawbars, similar to faders on an audio mixing board
The sound on a tonewheel Hammond organ is varied through the manipulation of drawbars. A drawbar is a metal slider that controls the volume of a particular sound component, in a similar way to a fader on an audio mixing board. As a drawbar is incrementally pulled out, it increases the volume of its sound. When pushed all the way in, the volume is decreased to zero.
The labeling of the drawbar derives from the stop system in pipe organs, in which the physical length of the pipe corresponds to the pitch produced. Most Hammonds contain nine drawbars per manual. The drawbar marked "8′" generates the fundamental of the note being played, the drawbar marked "16′" is an octave below, and the drawbars marked "4′", "2′" and "1′" are one, two and three octaves above, respectively. The other drawbars generate various other harmonics and subharmonics of the note. While each individual drawbar generates a relatively pure sound similar to a flute or electronic oscillator, more complex sounds can be created by mixing the drawbars in varying amounts.
Some drawbar settings have become well-known and associated with certain musicians. A very popular setting is 888000000 (i.e., with the drawbars labelled "16′", "5 1⁄3′" and "8′" fully pulled out), and has been identified as the "classic" Jimmy Smith sound.
Preset keys on a Hammond organ are reverse-colored and sit to the left of the manuals
In addition to drawbars, many Hammond tonewheel organ models also include presets, which make predefined drawbar combinations available at the press of a button. Console organs have one octave of reverse colored keys (naturals are black, sharps and flats are white) to the left of each manual, with each key activating a preset; the far left key (C), also known as the cancel key, de-activates all presets, and results in no sound coming from that manual. The two right-most preset keys (B and B♭) activate the corresponding set of drawbars for that manual, while the other preset keys produce preselected drawbar settings that are internally wired into the preset panel.
Vibrato and chorus
Hammond organs have a built-in vibrato effect that provides a small variation in pitch while a note is being played, and a chorus effect where a note's sound is combined with another sound at a slightly different and varying pitch. The best known vibrato and chorus system consists of six settings, V1, V2, V3, C1, C2 and C3 (i.e., three each of vibrato and chorus), which can be selected via a rotary switch. Vibrato / chorus can be selected for each manual independently.
The B-3 and C-3 models introduced the concept of "Harmonic Percussion", which was designed to emulate the percussive sounds of the harp, xylophone, and marimba. When selected, this feature plays a decaying second- or third-harmonic overtone when a key is pressed. The selected percussion harmonic fades out, leaving the sustained tones the player selected with the drawbars. The volume of this percussive effect is selectable as either normal or soft. Harmonic Percussion retriggers only after all notes have been released, so legato passages sound the effect only on the very first note or chord, making Harmonic Percussion uniquely a "single-trigger, polyphonic" effect.
Start and run switches
Console Hammond organs such as the B-3 require two switches; "Start" to drive the starter motor
and "Run" to drive the main tonewheel generator.
Before a Hammond organ can produce sound, the motor that drives the tonewheels must come up to speed. On most models, starting a Hammond organ involves two switches. The "Start" switch turns a dedicated starter motor, which must run for about 12 seconds. Then, the "Run" switch is turned on for about four seconds. The "Start" switch is then released, whereupon the organ is ready to generate sound. The H-100 and E-series consoles and L-100 and T-100 spinet organs, however, had a self-starting motor that required only a single "On" switch. A pitch bend effect can be created on the Hammond organ by turning the "Run" switch off and on again. This briefly cuts power to the generators, causing them to run at a slower pace and generate a lower pitch for a short time. Hammond's New B3 contains similar switches to emulate this effect, though it is a digital instrument.