Implementation of a Hammond organ synthesizer

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Dr. Rucz Péter
Department of Networked Systems and Services

The Hammond organ was created for the synthesis of the sound of pipe organs, and became a popular keyboard instrument, thanks to the unique and unexpected effects present in its sound. The Hammond-organ is used in all styles of music nowadays. The operation of the electro-mechanical instrument is based on magnetic pickups and revolving, specially moulded metal wheels, called tonewheels. The revolving tonewheels generate sinusoid waves at different frequencies, producing the harmonics of the voice. A rotating speaker, the so called Leslie speaker is also part of the Hammond-organ, which is responsible for its characteristic sound to a significant extent.

A remarkable disadvantage of the instrument is its large size and weight, that makes the user unable to transport it. This problem procured the demand for digital Hammond organ synthesisers. Despite the evolution of sound synthesis, reproducing the sound of the Hammond organ remained a great challenge, mainly owing to the effects created by the rotating speaker. One of these effects is the frequency modulation caused by the Doppler effect during the motion of the speaker.

In my thesis, I present the implementation of a real-time, controllable Hammond organ synthesiser plugin. First, I introduce the structure of the Hammond ogran and the Leslie speaker. In the following, I create the model of the instrument and the rotating speaker. Finally I implement the VST (Virtual Studio Technology) plugin based on the preceding work. Simulating the rotary speaker by means of the acoustic finite element method and incorporating the results into the plugin is an essential part of the thesis.


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