Hammond Organs 101 - How Do They Work?




In your DAW, you’ve probably got a virtual instrument with Hammond B3 organ sounds. A quality virtual instrument can emulate that classic organ quite accurately. But when it comes to understanding how a B3 works, it’s like that old Marvin Gaye/Tammi Terrell song says, “Ain’t nothin’ like the real thing, baby.” In this excerpt from Pro Member Mix Fix Ft. Mark Conner Part 1, you’ll see studio musician Dave Zerio and Fab Dupont explain the features of a B3 and how it makes sound.

Draw it Up

In the excerpt, Dave points out that a B3 has two motors. One to start it, and another “synchronous” motor that’s on all the time. The B3 is considered a “tonewheel organ” because of how it creates sound. The motor spins circular metal disks attached to magnetized rods, generating magnetic fields turned into audio signals by electromagnetic pickups. Each tonewheel has a varying number of tiny notches in it. The amount of gaps determines the pitch created. When you press a key, it completes the circuit for that note, and its signal gets sent to the output.

Adjusting the drawbars on the Hammond B3 organ at Flux Studios.

One of the features of a Hammond that seems mysterious to non-organ players is the drawbars. Dave explains that most of them create harmonics, adding tonal variety and complexity to the sine-wave-like fundamental tones that a B3 otherwise produces. The white drawbars create even harmonics, and the black ones are odd. The farther you pull the drawbar, the louder that harmonic will be blended into the signal.

If you’ve heard the word “percussion” in reference to a B3, it refers to a setting you can turn on and adjust with dedicated drawbars, which adds a harder attack that provides a more percussive sound to the notes.

The black-colored keys (with white sharps and flats) at the upper left of each manual (“manual” is what each keyboard on an organ is referred to) can be pressed to recall preset drawbar combinations. Those keys do not create any sound.

Each of the B3’s manuals offers five octaves of playable notes. They give the organist plenty of musical real estate to work with.

Besides the drawbars, another way to alter the tone in a B3 is to use the built-in vibrato and chorus effects. Dave says that some B3s allow you to turn these effects on and off independently for each manual. The organ he’s using in the demonstration features a switch with three intensity levels for the chorus and vibrato effects.

One of the most significant ways to impact a B3’s tone is to connect it to a Leslie rotating speaker cabinet. A Leslie features a rotating cylinder referred to as a “drum” at the bottom with a woofer facing into it and a rotating horn at the top with a high-frequency driver attached.

The signal is split at an 800Hz crossover point, with the lows going through the drum and the upper mids and highs through the horns. The Leslie utilizes the Doppler effect to create its pulsating sound. The horns and drum typically spin at different speeds from each other.

A look inside of a Leslie reveals the horn on top, the drum at the bottom and the power amp on the bottom left. By Hustvedt - Own work, CC BY-SA 3.0


The Leslie at Flux is a modified one controlled with a pair of foot pedals. A more typical setup is for the organist to control the rotary speed from switches to the lower left of the lower manual on the B3.

Not only does the Leslie function as an effect, but it’s also the amplifier for the organ. While most Leslie’s have an internal amplifier, the Leslie at Flux was modded so that you can connect an amp of your choice to it, which then gets sent through the rotating horns and drum.

A typical studio mic’ing setup on a Leslie features a stereo pair of mics on the horns. Typically, they’re aimed at the vents at the top of the side on the left and right. Sometimes, a pair of mics in a coincident stereo configuration such as XY is placed in front of the cabinet. That’s the configuration Fab uses in the video. Usually, the rotating drum gets mic’ed with a single microphone. Why not stereo mic it? It puts out mostly bass frequencies, which are best kept in mono to avoid potential phase problems.

As shown in this screenshot from the Rotary section of the UADx Waterfall B3 plug-in, two mics are often placed on either side of the cabinet to capture the horn part of a Leslie’s sound with one mic on the drum at the bottom.

Together Again

The Leslie gets its name from Don Leslie, who invented the rotating speaker concept back in the 1940s to help improve the sound of Hammond organs. He and Hammond’s owner Laurens Hammond ended up in a lifelong feud because the latter didn’t like Leslie’s invention and didn’t want it associated with the Hammond organ name. Part of Hammond’s issue was that his company had its own line of organ amplifiers, which Leslie’s competed with. Don Leslie even tried unsuccessfully to sell his company to Hammond.

But although Laurens Hammond wanted no part of Leslie speakers, organists loved the combination of the B3 and the Leslie. Despite Laurens Hammond’s best efforts, the two products became inexorably intertwined in the minds of musicians.

Ironically, both the Hammond and Leslie companies eventually did end up under the same corporate roof —Suzuki currently owns both. You can still buy Hammond organs, but they now use digital technology rather than the analog tonewheel style. Several models of Leslies are still made by Suzuki under the Hammond name.

Models and More

Although the Hammond B3 organ is the most well-known vintage Hammond organ, it’s not the only one with that distinctive sound. Two other models, the C-3 and A-100, feature the same internal circuitry as the B3. The main difference between all three is the shape and construction of their cabinets.

As for Leslies, perhaps the best know was the 122. It was housed in a 41” high wooden cabinet and included a 40W tube amp and a balanced output. It was made specifically for use with Hammond organs. Hammond-Suzuki makes several reissues of the 122, which you can buy new if you want. Another well-known Leslie was the 147, designed to work with any organ, not just Hammonds.

These days, other companies, such as Motion Sound, also make keyboard amps with rotating speakers. Most professional-level performance keyboards such as the Nord Stage 3 have excellent rotary speaker effects built-in.

Plug and Play

While there’s nothing like a genuine Hammond B3 organ and Leslie, virtual instrument emulations are often quite accurate. The UADx Waterfall B3 from Universal Audio is a recent example. It was meticulously modeled from a hardware B3 and it also includes a modeled Leslie 147.

The organ section of the UADx Waterfall B3 virtual instrument plug-in was used in the following examples.

Here are a couple of examples using the Waterfall B3 that show some of the Hammond B3 features discussed earlier.

The first example demonstrates the impact of the Leslie speed control on the B3 and consists of a four-measure figure that plays three times. The virtual Leslie is set on Brake the first time, so neither drum nor horn is spinning. The second time it’s on Slow, and the third time on Fast.

The next example shows the impact of the Percussion feature on the sound. It’s comprised of another four-measure figure that plays three times. The first time the percussion is off. The second time it’s on, but with the volume on Soft. The third time it’s on with the volume on Normal, which is louder.

Overdriving the tube in a Leslie can create some cool distortion effects. The third example shows off the modeled tube drive in the Rotary section of the Waterfall B3. You’ll hear yet another four-measure figure. This one plays twice. The first time with the plug-in’s Drive control off and the second time with up to about six.

If you want to get distortion from an actual B3 and Leslie, you do it with gain. You can adjust the preamp in the B3 and the volume control on the Leslie until you find the right amount of saturation.

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