I have a number of Moog synthesizers and want to understand HOW an oscillator makes sound. I have done the regular google searches but nothing really gets into detail specifically about how the sound is produced. One article actually said “an oscillator is a little box that produces sound”!!! That is the same as saying it happens by magic…
Does anyone have a link that explains in detail how sound is produced and picked up in an synth? Also is it fair to say that a synthesizer is picking up the sound of electricity?
When I just sit and listen to my synths it SEEMS like there is something actually making a physical sound, there is a pop and then a bunch of resonant frequencies that are produced by the pop sound. The filter seems to cut out the harshness of the pop sound and slowly cut off the harsher frequencies until only the resonance is left over. If I were hitting a buffalo drum, the pop would be when the mallet hits the drum and the resonance would be the vibrations of the drum that continue after striking it. It bothers me that I dont really know what is producing the sound in the first place.
The sounds a synth makes are actually electrical signals generated by it that are eventually converted back into actual sounds that our ears can hear by a speaker, either a loudspeaker a few meters away or headphone speaker close to our ear.
Those electrical signals go from negative energy to positive energy that, once converted back to sound waves in the air by a speaker, make our eardrums move back and forth which our brain interprets as sound.
Most of analog synthesizers use what is called a VCO (voltage controlled oscillator) that is based on a ramp generator. It is a circuit that charges a capacitor (think of it as a very small rechargeable battery) at a certain speed, and when a certain power level is reached, the circuit quickly discharges the capacitor and that creates a click sound (full of harmonics). And the cycle repeats. At what speed the cycle repeats will be the audio frequency generated by the circuit (when it will be converted back to air sound waves by a speaker) and is determined by a given voltage (hence the VCO name) that will change depending on what key you press on the keyboard. The waveform generated is called a Sawtooth, or ramp-up. Other waveforms are created by modifying that sawtooth with other circuitry, to get square, triangle, and some other ones too.
This is a very simplistic description of what goes on in an electronic oscillating circuit found in a typical analog synth.
Hope it helps a little.
Here’s an excellent video explanation of different oscillator circuits: