# Hammond organ and Leslie speaker: tonewheels, drawbars and rotors

> The Hammond organ explained: tonewheels, nine drawbars, B-3 percussion and vibrato, the console models, and how a Leslie speaker's rotors and cables work.

Canonical: https://sstsynths.com/hammond-organ-leslie
Updated: 2026-10-31

The Hammond organ is an electric organ first made in 1935 whose tones, until 1975, came from spinning metal tonewheels beside magnetic pickups. Nine drawbars mix them, the B-3 of 1954 added harmonic percussion, and a Leslie speaker's rotating horn and drum add the famous swirl.

## How tonewheels make the sound

Each basic tone of a Hammond comes from a **tonewheel**, a shaped metal wheel spinning in front of an electromagnetic pickup. The changing magnetic field induces a small alternating current close to a sine wave. All the tonewheels are geared to one synchronous motor, so every note stays at a fixed pitch relative to the others. Because the sound comes from moving parts, a tonewheel Hammond is strictly an electromechanical, not an electronic, organ. Around two million Hammond organs have been made; tonewheel models were built until 1975.

The design makes compromises. Its harmonics use the nearest frequencies the gearing provides rather than exact multiples, and the only guaranteed pitch is concert A at 440 Hz. Pickups also catch faint signals from neighbouring wheels (*crosstalk* or leakage), and keys can make an audible click. Hammond treated both as defects — in 1963 it added filtering to reduce crosstalk and mains hum — but players came to love them, and modern digital clones deliberately imitate them.

## Drawbars: additive synthesis on sliders

A **drawbar** is a metal slider that sets the volume of one pitch: pushed fully in it is silent, pulled out step by step to 8 it is loudest. Most Hammonds have nine drawbars per manual. Their labels come from pipe-organ stops, where pipe length sets pitch: 8′ is the fundamental of the note played, 16′ an octave below, and 4′, 2′ and 1′ one, two and three octaves above; the others add further harmonics. Mixing nearly pure tones like this makes the Hammond a kind of additive synthesizer.

*The nine drawbars of one manual, set to 888000000 — the first three fully out.*

A setting is written as nine digits, one per drawbar from 16′ to 1′. One of the most famous is **888000000**, with only the 16′, 5⅓′ and 8′ drawbars out, long associated with jazz organ. Organs made from 1969 have each drawbar's footage engraved on its end. Console models also have **presets**: an octave of reverse-coloured keys left of each manual, where C cancels the manual, B and B♭ switch to the two sets of drawbars, and the other keys call up combinations wired inside the organ.

## Vibrato, chorus, percussion and the start switch

- **Vibrato and chorus.** A rotary switch selects three vibrato settings (V1–V3) and three chorus settings (C1–C3), which mix the tone with a slightly detuned, moving copy. It can be enabled for each manual separately. The effect is made mechanically by a rotating metal scanner.
- **Harmonic percussion.** Introduced on the B-3 and C-3 in 1954, it adds a decaying second or third harmonic to the start of a note, normal or soft, to evoke harp, xylophone or marimba. It retriggers only when all keys have been released, so legato playing sounds it only on the first note or chord.
- **Start and Run.** On most models a Start switch spins a starter motor for about 12 seconds, then the Run switch is turned on for about four seconds before Start is released. Briefly switching Run off and on again slows the generator, giving a quick downward pitch bend.

## Console models, from the Model A to the B-3

Console Hammonds have two 61-note manuals and a pedalboard of at least two octaves, and most need an external amplifier and speaker cabinet. Spinets have two 44-note manuals, one octave of pedals and built-in speakers. Most console pedalboards have 25 notes, because the top notes of a 32-note church pedalboard were seldom used.

**Landmark Hammond console organs**

| Model | Introduced | What it added |
| --- | --- | --- |
| Model A | June 1935 | Two 61-key manuals, 25-key pedalboard, expression pedal and preset keys; US$1,193 |
| BC | December 1936 | A chorus generator: a second tonewheel set adding slightly sharp or flat tones |
| C | September 1939 | The same internals in a closed cabinet with "modesty panels" for church use |
| B-2 / C-2 | 1949 | Vibrato could be switched on each manual separately |
| B-3 / C-3 | 1954 | Harmonic percussion; made until early 1975; the B-3 cost US$2,745 in 1955 |
| A-100 | 1959 | A self-contained B-3/C-3 with built-in amplifier and speakers |

The B and C cabinets share the same internals; the C's closed front and sides suited churches. The last B-3s and C-3s were assembled from leftover parts and are not considered as good as earlier ones. After tonewheels ended Hammond made transistor organs, went out of business in 1985, and the name passed to Suzuki, whose Hammond-Suzuki released a digital "New B-3" in 2002. Lighter digital "clonewheel" organs from Korg, Roland and Clavia, and software, emulate the tonewheel sound.

## The Leslie speaker: horn, drum and Doppler

A **Leslie** is an amplifier and loudspeaker in one cabinet that moves the sound around. A crossover set at 800 Hz splits the signal: treble goes to a compression driver whose sound leaves through a rotating horn, bass to a woofer firing into a rotating drum. As the sources spin, the Doppler effect shifts the pitch up and down and the volume rises and falls, which is the swirling sound. The switch on the organ has two speeds, *chorale* and *tremolo*, and the moment of changing between them is part of the effect.

*Approximate rotor speeds of a Leslie on its two settings.*

**Common Leslie models**

| Model | Details |
| --- | --- |
| 122 | The most popular: 41 in (1,000 mm) tall, 40 W valve amplifier, one 15-inch woofer, balanced input that resists hum; designed for console Hammonds |
| 147 | The "universal" 122 for many organs: unbalanced input and a different speed control |
| 142 / 145 | Smaller 33-inch (840 mm) versions of the 122 and 147 |
| Pro-Line (760, 820, 900, 910) | Louder solid-state models on casters for 1970s touring; the 820 has a single rotor |
| 122A, 147A, 2101 | Modern Hammond-Suzuki models; the 2101 has line inputs and MIDI control of its settings |

The speaker was sold from 1941 as an add-on, first for Hammonds and then for other organs; Hammond at first declined to sell it and even changed its connectors to block it. The Leslie business was sold to CBS in 1965, Hammond began officially supporting the speaker the following year, the T-200 spinet of 1968 was the first Hammond with a Leslie built in, and Hammond bought Leslie in 1980. Suzuki has owned the name since 1992.

## Cables, power and miking

A Leslie does not use a jack lead. An Amphenol connector carries AC power, audio and the speed control together: older valve models use six-pin connectors, later ones nine-pin, and modern ones 11-pin with separate IEC mains leads. Pin layouts differ between organs and speakers, and a badly wired cable can permanently damage the organ or the speaker — or electrocute someone. Connecting a vintage Leslie to anything other than an organ needs a *combo preamp*, which merges mains and line signal and adds a speed footswitch.

> **Voltage and frequency both matter** Because the tones come from a synchronous motor, Hammond built different tonewheel organs for 110 V/60 Hz and 240 V/50 Hz mains, with different gearing and starter motors (1,200 and 1,500 rpm). A step-down transformer alone does not fix the frequency; third-party adapters let touring bands run one region's organ in the other.

Because a Leslie modifies the sound as well as amplifying it, its output cannot simply be fed to a bigger PA. Instead it is miked: a typical live setup puts two microphones on opposite sides of the horn and one on the drum, and a popular studio recommendation is two dynamic microphones on the horn and one on the drum. A 122 has only a 40 W amplifier, so miking is how it reaches a large room.

## Frequently asked questions

### What is the difference between a Hammond B-3 and a C-3?

Their internals are the same; both were introduced in 1954 with harmonic percussion. The C-3 has a closed cabinet with front and side "modesty panels" for church use, while the B-3 has an open stand.

### What do the drawbar numbers on a Hammond mean?

Each of the nine drawbars sets the volume of one pitch from 0 (in) to 8 (fully out). A registration is written as nine digits from the 16′ drawbar to the 1′ drawbar; 888000000 means the first three are fully out and the rest are in.

### Can a US Hammond organ be used in Europe?

Not directly. Tonewheel Hammonds were built for either 110 V/60 Hz or 240 V/50 Hz, with different gearing, because their pitch depends on the mains frequency. Third-party adapters exist for touring bands.