The Oscillator Section
What does the oscillator do?
As already mentioned in the previous section, the oscillator is the part of the synth that generates the basic raw sound.
The main oscillator usually refers to a "keyboard-controlled oscillator", that may sound technical but it basically means is that, when you play a note on the keyboard, the oscillator will generate a cyclic waveform at that intended pitch (for as long as you hold down that note on the keyboard). If you press A3, the waveform will be generated at a rate of 440Hz (440 cycles per second).
In short, the keyboard controls the pitch of the oscillator (hence, keyboard controlled oscillator).
On a synthesiser, the oscillator is often labeled Oscillator or simply ‘OSC', ‘VCO', ‘DCO', ‘Waveform' or ‘Waveshape'.
Oscillators on early analog synths were controlled by analog voltage - VCO, which tended to make their pitch rather unstable, and sometimes drifting out of tune.
Later, analog and digital synthesisers started to use digital controlled oscillators - DCO, Digital Controlled Oscillator, which are far more stable in pitch.
Waveforms and their Spectrum
The waveform is the 'shape' of the output produced by the oscillator. It determines how the oscillator will sound - in particular how 'bright' it sounds. The brightness is actually determined by the number and type of harmonics present in the waveform. You can hear the difference between waveforms because they each have a distinct sound, which is determined by their harmonic content.
There are a number of standard waveforms such as SINE, TRIANGLE, SQUARE, SAW TOOTH & NOISE, but computer-based oscillators can generate all sorts of weird and wonderful wave shapes.
Below is a list and description of the most common sound waves found in nearly every 'analog' synth: Sine Wave: A Sine wave is the most basic waveform, it has no harmonics (overtones) at all. It only has the tone of the fundamental frequency and no timbre. The Fundamental frequency is the base or root frequency, which we identify as pitch (eg "A3" would be at 440Hz). The sine wave has a very pure tone, almost flute like, this is often the waveform loaded as default in most synth when you want to create a sound from scratch. This is a great waveform for subbass & low kicks (808 like).
Triangle Wave: Sounds (and looks) a bit like the sine wave but has some hollow-sounding quiet overtones. The filter will have little effect on these waveforms (sine & triangle) as there are no harmonics to be acted upon.
Square or pulse Wave: A Square wave has very sharp corners. It has a hollow sound with quite strong overtones. It is made up of only odd numbered harmonics. On many synths, you can vary the pulse width of the wave, this is the ratio of the on part to the off part. Technically, when the ratio is 50-50, this is a square wave, but if the ratio of on / off differs, this is called a pulse wave, also known as rectangle. However most synths tend to label it either square or pulse. By increasing the pulse width, the sounds becomes brighter and richer; but as the Pulse Width becomes very narrow, it becomes more thin and nasal.
Sawtooth wave: This is a very 'bright' 'fizzy' sounding waveform (it actually contains all the odd and even harmonics of the original frequency). It is very good for trebly sounds & dramatic filter sweeps (because it is so bright, the filter has something to work on).
Noise Wave: This is isn't a 'tone' at all, but a random mixture of all frequencies. It sounds like the sort of hiss you get on a radio when you're not tuned into a station. There are two types of noise - white noise, which is truly random and pink noise, in which the lower frequencies get more emphasis (this produces a 'heavier' hiss). Noise is good for generating percussive sounds like snares & hi-hats, for simulating wind or sea sounds (when put through a filter modulated by an LFO).
How many oscillators?
Some synths have only one oscillator, but many synths have two or three (some have more). You can generally get a much 'fatter' sound with two or more oscillators and create more interesting texture. For example, you can set them an octave apart to thicken the sound, or you can detune them very slightly to produce a chorus effect. Single oscillator synths often use pulse width modulation on the square wave to produce a similar result.
Synths with one only oscillator are usually better suited for bass sounds or lead and riffs, like the classic Roland TB303 for example. For more atmospheric sounds and pads, synths with several oscillators are usually more appropriate for the job. ES 1 is a two-oscillator synth, whereas ES 2 provides three oscillators (in fact it gives you 4, but more on that later!).
Oscillator pitch
We have already discussed how oscillators are controlled by the keyboard, so that when you press the note A3, the oscillator plays an A. However, most oscillators also have a pitch/ range control, which lets you set the basic pitch of the output.
It usually works like an octave up/down control, and can vary from 16-8-4. A range set to 16 will be a lower pitch, while a range set to 4 will create a higher pitched sound. Therefore if you want a sub bass sound set your oscillator to a Sine wave and a range of 16, or for a higher pitched sound, such as a flute type sound, set your oscillator to a Sine wave with range of 4.
ES2 Oscillators
Let’s take a look at the ES2. You'll find it has a higher quality sound than the ES1, although that doesn't necessarily mean its always going to be the best synth for the job in hand. You'll also notice it looks a bit more complicated than the ES1, but over the next couple of weeks you'll become much more familiar with it and discover its creative potential!