The Hammond organ is an electric organ invented by Laurens Hammond in 1934 and manufactured by the Hammond Organ Company. While the Hammond organ was originally sold to churches as a lower-cost alternative to the wind-driven pipe organ in the 1960s and 1970s, it became a standard keyboard instrument for jazz, blues, rock music, church and gospel music.
The original Hammond organ used additive synthesis of waveforms from harmonic series made by mechanical tonewheels that rotate in front of electromagnetic pickups. The component waveform ratios are mixed by sliding drawbars mounted above the two keyboards. Although many different models of Hammond organs were produced, the Hammond B-3 organ is most well-known. In the late 1960s and throughout the 1970s the distinctive sound of the B-3 organ (often played through a Leslie speaker) was widely used in Blues, progressive rock bands and blues-rock groups. The last electromechanical Hammond organ came off the assembly line in the mid-1970s.
In the 1980s and 1990s, musicians began using electronic and digital devices to imitate the sound of the Hammond, because the vintage Hammond organ is heavy and hard to transport. By the 1990s and 2000s digital signal processing and sampling technologies allowed for better imitation of the original Hammond sound.
In 1897 Thaddeus Cahill patented an instrument called the Telharmonium (or Teleharmonium, also known as the Dynamaphone). Using tonewheels to generate musical sounds as electrical signals by additive synthesis, it was capable of producing any combination of notes and overtones, at any dynamic level. This technology was later used to design the Hammond organ.
About 30 years later American engineer and inventor Laurens Hammond filed U.S. Patent 1,956,350 for a new type of “electrical musical instrument” that could recreate a pipe organ-type sound. He got the idea for the tonewheel by listening to the moving gears of his electric clocks and the tones produced by them. He understood the fact that every instrument sounds the way it does because of its many harmonic overtones and their varied intensities. The invention was unveiled to the public in April 1935 and the first model, the Model A, was made available in June of that year. The organ was first used for popular music by Milt Herth, who played it live on WIND (AM) soon after it was invented. Radio shows of the 1930s and 40s used the Hammond for not only mood music but more significantly, for sound effects. For example, if you wanted a clock chime, you would set the drawbars at 010010603. The Hammond organ was widely used in United States military chapels and post theaters during the Second World War, and returning soldiers’ familiarity with the instrument may have helped contribute to its popularity in the post-war period.
Hammond had intended his invention to be an affordable substitute for pipe organs, as a replacement for the piano in middle-class homes, and as an instrument for radio broadcasting. However, by the 1950s, jazz musicians such as Jimmy Smith began to use the organ’s distinctive sound. By the 1960s, the Hammond became popular with pop groups and was used on the British pirate station Radio 390. In Britain the organ became associated with elevator music and ice rinks music. However, the overdriven sound of the Hammond gained a new image when it became part of 1960s and 1970s rock with artists like Gregg Allman, Steve Winwood, Keith Emerson, Jon Lord, Matthew Fisher, and Rick Wakeman.
Hammond is now owned by Suzuki Musical Inst. Mfg. Co., Ltd., and distributed by Hammond Suzuki Co., Ltd. Today, Hammond build electronic organs that closely replicate the tonewheel organ sound using current technology.
The original Hammond organ imitated the function of a pipe organ’s ranks of pipes in multiple registers by using additive synthesis of waveforms from harmonic series to generate its sounds. The Hammond organ’s individual waveforms are made by mechanical tonewheels that rotate in front of electromagnetic pickups. Each tonewheel assembly creates audio with low harmonic content, close to a sine wave (the sound of a tuning fork). Inside the coil is a permanent magnet. As the teeth of the tonewheel pass by, the strength of the magnetism changes—when the tip of a tooth is closest to the tip of the magnet, the magnetism is strongest. As the magnetism varies, that creates AC in the coil, which becomes one of the frequencies used in harmonic synthesis. The tonewheel illustrated has, comparatively speaking, many fine teeth, and would generate a relatively high frequency. (You might need to magnify the image to see the teeth easily.) Historically, this device, known in the late 19th Century, was called a “phonic wheel”.
Although they are generally included in the category of electronic organs, original Hammond organs are, strictly speaking, electric or electromechanical rather than electronic organs because the waveforms are produced by mechanical tonewheels rather than electronic oscillators. Hammond organs use 96 tonewheels. Five of these are blanks, only present in order to balance out the rotating mechanical sub-assemblies. Thus the tonewheel assembly generates 91 frequencies, which are all that are required for the entire organ. The appropriate frequency outputs, nine per key, are routed to the key contacts for each note on the keyboards (generally referred to as manuals).
Strictly speaking, the Hammond organ has technical compromises, because the harmonics of any given fundamental are likely not to be exact multiples of the fundamental. One source (identity long lost) said that true and accurate harmonic synthesis would require about 4,000 frequencies. The Hammond organ uses the nearest-available frequencies, which has some part in creating its distinctive tone color.