The synth voice
Oscillator, filter, amplifier, envelope — the four-stage chain behind nearly every synthesizer.
A lone oscillator is just a drone — hold it and it never changes. To turn a tone into a note, the sound travels down a short chain, and almost every synthesizer ever built uses the same four stages.
The oscillator makes a raw tone; the filter shapes its brightness; the amplifier controls its loudness over time; out it goes.
Oscillator → filter → amplifier
The oscillator makes the raw waveform. The filter removes or emphasises harmonics to change the colour — the heart of subtractive synthesis. The amplifier sets how loud the note is at each moment. On its own, though, that chain still switches on and off abruptly. What makes it feel alive is the last piece.
The envelope: ADSR
An envelope is an automatic hand on the volume knob. The classic shape has four stages — Attack, Decay, Sustain and Release — and it is the difference between a soft pad that swells in and a sharp pluck that stabs and fades. Drag the four sliders below and play a note to feel it.
- Attack — how long it takes to reach full volume after a key goes down. Fast is a pluck; slow is a swell.
- Decay — how quickly it drops from that peak to the sustain level.
- Sustain — the volume it holds at while the key stays down (a level, not a time).
- Release — how long it takes to fade to silence after the key is let go.
Fast attack and short release make a plucky lead; slow attack and long release make an evolving pad — the same oscillator, a completely different instrument.