Synthesis
Synthesis creates sound by generating and shaping signals. In a simple subtractive synthesizer, an oscillator supplies the starting tone, a filter changes its frequency balance and an envelope shapes how it develops over time. Learning those roles makes a patch easier to adjust on purpose.
- Choose a source
- shape its spectrum
- control its movement
Where you run into this
- Synthesizers
- Electronic production
- Sound design
What changes when I switch waveform?
An ideal sine wave contains one frequency. A sawtooth contains a series of harmonics above its fundamental, giving a brighter starting sound. Square and triangle waves have different harmonic balances, so they can sound different at the same pitch.
The waveform supplies material for the rest of the patch. A filter applied to a rich sawtooth has more harmonics to reshape than the same filter applied to a sine. Your choice of source matters before you add modulation.
What do the main building blocks do?
- Oscillator
Generates the source signal. Its pitch and waveform determine the starting note and spectral content.
- Filter
Changes the balance of frequencies. A low-pass filter reduces higher-frequency content as its cutoff is lowered.
- Amplifier envelope
Shapes the level through the note, from its onset to its release. It helps distinguish a short pluck from a sustained sound.
What does ADSR mean?
A common envelope has four stages. It can control amplitude or another destination, such as filter cutoff.
| Stage | What it controls | A useful comparison |
|---|---|---|
| Attack | Time to rise from the starting level to the peak | Immediate onset versus a gradual fade-in |
| Decay | Time to move from the peak to the sustain level | A quick drop versus a slower settling |
| Sustain | The held level while the note continues | Low remaining level versus a strong sustained tone |
| Release | Time to return toward zero after the note ends | A short cutoff versus a lingering tail |
Sustain is a level, not a duration. Sound Design puts envelopes to work on real sounds.
Build a simple pluck on your synthesizer
- Start with one oscillatorChoose a sawtooth and a simple initial patch. Turn off additional layers so you can hear each change.
- Shorten the amplitude shapeUse a fast attack, a short decay, a low sustain level and a short release. Hold a key and listen to the note fade.
- Shape the brightnessLower the low-pass cutoff until the sound is less bright. If available, use a short filter envelope to give the beginning more brightness than the tail.
- Test it in a phrasePlay several short notes at the intended tempo. Adjust the release if adjacent notes overlap more than you want.
How is an LFO different from an envelope?
An envelope usually follows a triggered contour: it begins with a note and progresses through its stages. A low-frequency oscillator, or LFO, supplies repeating movement.
For a simple comparison, use an envelope to open the filter at the start of each note, then use a slow LFO to open and close it repeatedly during a held note. The destination is the same; the movement has a different shape.
How do synthesis methods differ?
| Method | Main idea | A sound to explore |
|---|---|---|
| Subtractive | Filter a harmonically rich source | A plucked or sustained tone with changing brightness |
| Additive | Combine individual frequency components | A tone whose partials change independently |
| FM | Use one oscillator to modulate another at audio rate | A tone that becomes brighter or more metallic as modulation increases |
| Wavetable | Read and move between stored waveforms | A sustained note with an evolving spectrum |
| Granular | Recombine very short pieces of sound | A stretched or scattered texture |
Many instruments combine methods. A wavetable oscillator can feed a subtractive filter, and a sample can become the source for granular processing. Use the method that gives you useful control over the sound you are trying to make.
Which parameter should I change first?
Describe the problem in audible terms. If the onset is too slow, inspect the amplitude attack. If the note is too bright throughout, inspect the source and filter. If it continues too long after release, inspect the amplifier release and any effects tail.
Make one change and play the same phrase again. That comparison teaches you more than turning several controls before listening.