The original Hammond Organ was Designed and built by the ex-watchmaker Laurens Hammond and John M Hanert in April 1935. Hammond set up his ‘Hammond Organ Company’ in Evanston, Illinois to produce electronic organs for the ‘leisure market’ and in doing so created one of the most popular and enduring electronic instruments ever built. Hammond’s machine was designed using technology that relates directly to Cahill’s ‘Telharmonium’ of 1900, but, on a much smaller scale. The Hammond organ generated sounds in the same way as the Telaharmonium, the tone wheel-The tone generator assembly consisted of an AC synchronous motor connected to a gear train which drove a series of tone wheels, each of which rotated adjacent to a magnet and coil assembly. The number of bumps on each wheel in combination with the rotational speed determined the pitch produced by a particular tone wheel assembly. The pitches approximate even-tempered tuning.
This method of creating tones was maintained until the mid 1960′s when transistors replaced tone wheels
The Hammond had a unique drawbar system of additive timbre synthesis (again a development of the Telharmonium) and stable intonation – a perennial problem with electronic instruments of the time. A note on the organ consisted of the fundamental and a number of harmonics, or multiples of that frequency. In the Hammond organ, the fundamental and up to eight harmonics were available and were controlled by means of drawbars and preset keys or buttons.A Hammond console organ included two 61-key manuals; the lower, or Great, and upper, or Swell, and a pedal board consisting of 25 keys. The concert models had a 32-key pedalboard. Hammond also patented an electromechanical reverb device using the helical torsion of a coiled spring, widely copied in later electronic instruments.As well as being a successful home entertainment instrument, The Hammond Organ became popular with Jazz, Blues and Rock musicians up until the late 1960′s and was also used by ‘serious’ musicians such as Karheinz Stockhausen in “Mikrophonie II”