Synthesizers
Created | Updated Dec 14, 2004
Basically, a synthesizer is an electronic instrument which generates its own sounds from scratch by generating a wave and then giving it its tonal and volume characteristics using filters and amplifiers. This means that the sound in a synth can be tweaked almost infinitely and on newer synths you can save several sounds for recall without having to move all the parameter dials.
A synthesizer consists of three basic parts, the oscillators, the filters and the amplifier. The idea is is that the oscillator creates a sustained electrical waveform, let's say its a sinewave1, at a certain pitch. The filter colours the wave, gives it its character, its isness. The amplifier then determines the envelope of the wave, the 'shape' of how a sound is actually heard.
As an example, I'm going to use my synth, an Oberheim OB12. The synth has two oscillators, each of which can produce and mix three wave shapes, sawtooth, triangle or squaretooth2. The signal from these go to the 'oscillator mix' section where the balance between the oscillators is set as well as the balance from the ring modulator and the white noise generator.
The balanced signal then goes to the filter section. The OB12 has two filters which can be routed in either series or paralel and can be set as either low-pass, band-pass, high-pass or 'off'. The first filter has dials to control the filter frequency and resonance and there is a switch to chose between routing the filters in series or in parallel.
A high-pass filter allows frequencies above the filter frequency value through. Similarly, the low-pass filter allows frequencies below this value through and the band-pass filter allows through frequencies at this value. The resonance dial can best be described as an intensity, or brightness parameter. High values often result in squealing feedback3.
The next stage is the amplifier section. The main controls here are Attack, Decay, Sustain and Release (ADSR). These relate to how the volume of the sound changes as the note is played. Attack is how long it takes the sound to reach maximum volume from when the key is pressed.........
