Synthesizers have been around since the early 1970s and continue to inspire people to make music all over the world in software and hardware form. With hundreds of incarnations and variations, what sets them apart from each other is the design, integration and the methods of control. But at their heart, all synths are made up of the same building blocks.
Knowing a little bit about each major synth part will help you understand what you’re hearing and how it was accomplished. At its simplest, a synth is a oscillator, filter, amplitude envelope, and LFO. Let’s have a look at how those core components of every synthesizer come together to create sound.
An oscillator is the sound generating part which all other elements are built around. One oscillator is required to generate a sound, but synths tend to have multiple oscillators that can be mixed and merged to create interesting timbres and tones.
Each oscillator makes a sound which can be defined first by its waveform; a cycle of sounds measured in Hertz (cycles per second) which make the sound high or low pitched. The shape of the oscillating signal is what adds different traits to a sound. Here are some examples of common waveforms and their characteristics:
Sine – a soft, smooth waveform often used for basses.
Triangle – Similar sonic characteristics to a Sine Wave, with slightly sharper sound.
Saw Tooth – a thick sounding waveform, perfect for leads and basses.
Square – a tough, edgy waveform associated with chiptunes due to its raw-digital character.
Sample and Hold – a random collection of ever-changing frequencies which can be likened to the sound of R2D2 talking.
Each oscillator can be set to a particular octave. A sub-oscillator for example, will operate one octave below the rest to make the signal thicker and more bassy! Other settings allow the oscillator to be tuned; by semitone (to create chord combinations), or by cents (to create close or wide harmonics) which alter the interplay and overall sound of the synth.
A filter allows some but not all of the frequencies of the oscillator to be heard. If you want to make a sub-sonic rumble like you hear at the cinema, a Low Pass filter is required. This excludes high frequencies, enabling you to hear only low-frequency sounds. A High Pass filter does the opposite, allowing high frequencies to be heard while omitting the lows. The point at which the sound is passed or omitted is called the Cutoff Frequency.
There are many other types of filtering. For instance, a Band Pass filter gives you a segment in the middle to allow through, while a Notch filter allows all frequencies through, but boosts at the point the filter frequency is set.
To control the behavior of the sound and affect its volume over time as a key is pressed an Amplitude Envelop is used. Each synth has Attack, Sustain, Decay and Release settings to get the character you want.
This is useful for mimicking natural sounds. The sound of a note played on a violin slowly rises as its bowed, which we call the Attack of the sound. The Decay and Sustain regulate how loud the sound is as you hold it, and how long it remains at that level. An instrument like a xylophone has a short Decay and Sustain time, as you are unable to continuously hold the sound. Release is illustrated when you strum a guitar — the sound rings out, whereas if you hit a snare drum, the sound is released very quickly. Use these ADSR settings to define how your sound plays!
Low Frequency Oscillator
A Low Frequency Oscillator (LFO) is an oscillator you can’t hear, but affects another parameter of the synth. This is most commonly used for vibrato, making the sound wobble and vibrate at a speed you define. This is a particularly pleasing effect, with controls for depth (or range) of the LFO, frequency (speed), delay (amount of time before the effect is heard) and (like the main oscillator) a choice of waveform to shape how it affects the sound. Depending on the destination of the LFO, it could affect the Filter Cutoff Frequency (think of the dubstep wobble), Amplitude (like a Wah-wah pedal), Panning and a host of other parameters.
Those are the main parts of a synth, but what else is there?
Modulation gives you control over many aspects of the synthesizer, from radical pitch changes as you press a key, to how smoothly changes are made as you move the pitchbend wheel. The modulation wheel at its side is commonly used to assign custom controls, which can include filter frequency, LFO depth or overall volume. The best synths have a multitude of modulation options.
Effects may be built into a Synth to provide on-board distortion, cathedral-esqe reverbs or phattening choruses to enhance the sound. These are usually supplied with a Wet/Dry element, allowing you to mix the effected signal with the original synth sound.
Arpeggiators allow notes or chords to be held, making the synth trigger them in rhythmic patterns and rotating sequences. If you imagine the introduction to Visage – Fade to Grey or Donna Summer – I Feel Love, you’ll hear an arpeggiated part which allows a musician to make subtle and detailed adjustments to the sound elsewhere.
Every synth is different, that’s what makes them so unique! Knowing how they work is key to choosing the one that suits you, enabling you to decide the features and style of sound you need when making the future of music!
You’ll find all kinds of Synths on the Tindie page here.
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