Most synthesizer sounds, especially on classic analog and virtual-analog instruments, are built through "subtractive synthesis" - starting with a harmonically rich raw waveform and shaping it down.
Oscillators: the raw sound source
An oscillator generates the initial waveform before any shaping happens. Common waveform choices include:
- Sawtooth: bright and buzzy, rich in harmonics - a common starting point for leads and basses.
- Square/pulse: hollow, reedy character; pulse-width modulation on this waveform creates a classic thickening/chorus-like movement.
- Triangle: softer, fewer harmonics - closer to a pure tone, often used for sub-bass or gentle pads.
- Sine: the purest tone with no additional harmonics.
Filters: shaping the tone
A filter removes or emphasizes parts of the oscillator's frequency content - most commonly a low-pass filter, which progressively cuts higher frequencies as its cutoff is lowered, making a bright sawtooth sound duller and warmer. Filters are usually paired with an envelope (see our separate ADSR article) so the tone changes dynamically over the course of each note, not just statically.
Together, oscillator choice and filter shaping account for most of what makes one synth patch sound bright, dark, thin or fat - understanding both is the fastest way to start programming sounds rather than only using presets.
