Synthesis Essentials: All About Oscillators

Oscillators. The raw sound source that spawns the diverse range of tones and timbres spewed by all synthesizers. They come in different shapes and can be produced by a variety of techniques to make your imagination audible. If you consider the fact that all of the sounds we hear are vibrations in air, oscillators are creating synthetic vibrations that become sound once connected to a speaker. Instead of moving back and forth like a guitar string, the oscillator cycles between positive and negative voltages.

If these cycles take place between 20 and 20,000 times per second they are audible to the human ear. The rate of these fluctuations determines the frequency, or pitch of the tone, and this is tuned to produce the notes struck by the keys. We call one full fluctuation a cycle, or period, and refer to the shape that these oscillations take as a waveform. The shape of the oscillation determines the timbre or tone of the sound.

 Types Of Oscillator

Sine, Triangle, Sawtooth, and Pulse (or Square) are the four most commonly utilized synthesizer waveforms. Sine waves represent the pure tone of a single frequency, which is called the fundamental. The other waveforms have added harmonics or overtones that take place above the fundamental. This can add brightness, complexity and texture to the sound. Sawtooth waves are the most harmonically rich, because they have harmonics every integer above the fundamental. Therefore a sawtooth wave played at 100Hz will have harmonics at 200Hz, 300Hz, 400Hz and so on. Each successive harmonic descends in amplitude, or volume, by half and this cascade creates the descending sawtooth shape.

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