Any true rock and roll fanatic has heard the sounds of a Hammond Organ. Whether you realize it or not, the Hammond Organ has been very prominent in the sounds of rock and roll history.
Now, I'm not talking about those little "Hammond Pipers" that they used to demonstrate in the music stores in malls. I'm not talking about anything with Large Scale Integrated Circuits (LSI). I'm talking about the real deal. The Hammond B3 organ. Actually, I am talking about any of a series of Hammond Organs known as the "tone-wheel" organs. These organs are named because of the way they generate their sound. A tone-wheel Hammond organ is an amazing piece of machinery. Yes – I meant that. Machinery. Take a look inside one and you will see motors, gears, and all sorts of other mechanics that you will never see inside of a modern day keyboard. A Hammond Organ even has a start-up procedure! Because of that, no modern day keyboard can achieve the sound of a Hammond tone-wheel organ. Many have tried, all have failed. Now – let's be realistic. A Hammond B3 or other similar Hammond weighs upward of four hundred pounds. So – many keyboard players are willing to say that their lightweight Hammond emulator or synthesizer is a "good enough" imitation to not carry a real Hammond around. But – the real deal players carry the real thing for a reason. No imitation is good enough.
The Hammond organ generates its sound by a series of metal "tone-wheels". The wheels have gear teeth on them and they pass by an electromagnetic pickup. Each note is created, then, through an old fashioned implementation of additive synthesis where a number of tone-wheels are combined together to create a note complete with the desired partials. The partials are controlled by a set of drawbars that the organist uses to sculpt their tone.
While everyone clamors to get a "Hammond B3", if the sound is the only goal, then they should be a bit more broad-minded. The Hammond B3 is encased in a cabinet with four spindle legs. This makes the cabinet easier to carry than some other configurations. The Hammond C3, for example, is exactly the same internals as a B3, but it is in a different cabinet. The cabinet is more of a console. Some say that the "C" stands for "church" in that the cabinet hides the organist's legs. The C3 is a bit more difficult to carry around than a B3, but it does achieve the same sound. SO, if you are in a recording studio, or somewhere that the Hammond can stay stationary, a C3 will do you quite nicely. Another Hammond with the same internals is the A-100 series. These have the same organ internals as a B3 or C3, but also some internal amplifiers and speakers. Thus, they also are quite useful in a stationary environment like a studio.
Older models of Hammond organs use a very similar set of internals. The Hammond B2, C2, and others have basically the same sound environment, but they lack the Hammond "percussion" circuitry. By "percussion" I don't mean those horrific drum machine like things that were in the little Piper organs and other nonsense. This percussion is that characteristic percussive "chirp" that gives a Hammond one of its characteristic sounds. Percussion can be added to a B2 or C2. As a matter of fact there is a company that is well know because they make a device called the TREK Percussion that you can add to your B2 or C2, essentially turning it into a B3 or C3.
The Leslie Speaker
A HUGE part of the Hammond organ sound is the result of the Leslie Speaker. A Leslie speaker has a stationary bass speaker that faces into a rotor that can spin around at the organist's command. There is also a horn that spins around adding to the sound. The organist (depending on the particular Leslie model and its configuration) can set the rotors to "OFF", "CHORALE" (slow), or FAST. A key part of playing a Hammond organ is knowing when and how to change speeds on your Leslie for the desired effect. It is especially important how the Leslie spins up to speed, and slows down. For more detail on the Leslie speaker, see the related article.