Oscillators get to the very fundamentals of music and sound itself. It’s important to understand their role in sound composition as well as music itself, so let’s talk about what is an oscillator in music.
What is an Oscillator in Music
An oscillator is a single cycle, basic wave form which is looped at an incredibly high rate to reproduce a specific pitch. The pitch is typically determined by whichever note you’re playing on your midi keyboard.
This is essentially how a synthesizer constructs (or synthesizes) an audible tone.
The shape of this wave form determines the tonal characteristics of the sound as we perceive it.
Generally the rounder and more symmetrical the wave form, particularly when it resolves, the smoother the tone will be.
Here I’ve opened Xfer Records’ Serum, an Advanced Wavetable Synthesizer which allows us to create wave forms out of any shape we can imagine. It’s excellent for creating our own synth sounds from the ground up, but it’s great for demonstrating what is an oscillator in music, as well.
One of the presets allows you to cycle through all of the most basic wave form shapes.
The shape of the sound wave itself determines the sound.
The Shape of Sound Waves
As I covered in my break down of the various parts of a sound wave, the wave length ultimately determines the pitch.
Longer waves move more slowly, and the number of cycles per second determines the frequency.
Duplicating the same shape and fitting both in the same cycle will pitch the sound wave up an octave in that key.
The dynamic range between the extremes in the wave dictates how much energy is behind the sound wave. More energy hits our ear drums harder which we perceive as being louder.
The shape has everything to do with how we perceive it sonically.
There are a number of different shapes for sound waves:
Pictured above is a sine wave – a symmetrical sound wave with a gentle sloping shape.
The characters of the sound itself of the sine wave mirror the shape in many ways.
A sine wave sounds round and smooth, just like the curves which make it up.
What if we ditch the curves altogether? A sound which has a lot in common with the sine wave is the triangle wave:
While the wave form culminates in sharp peaks, the transitions between them are still uniform. More than that, it still ends at the same point it began at.
This creates a similar sound to the sine wave, albeit a bit brighter in the triangle.
If we’re building an oscillator wave form, it doesn’t have to end at the same point it began at.
The square wave is a good example of this. We get two polar opposite joined by the most abrupt break in the middle.
The result is a rich, bright, and interesting tone which you can get a lot of unique lead sounds from with some tweaks.
The more we get away from the smooth transitions and symmetry of the sine wave, the more dissimilar the oscillator begins to sound.
Generally, the more asymmetrical a sound wave’s shape, the sharper or harsher it will sound.
One final basic wave form to consider is the saw wave or sawtooth wave:
The wave form (when repeated) resembles the blades of a saw tooth, hence the name. Like the square wave, the sawtooth wave repeats at the opposite amplitude. This lack of symmetry creates a harsh and bright tone which at lower frequencies makes for a good synth bass.
Creating oscillators is the basis of audio production for those who work with wave tables.
While many of us just focus on “analog” instruments and don’t think about this, it’s still exciting to think that you can create a sound that no one has ever heard of before simply by designing a unique oscillator!