Basic Subtractive Synth

A saw wave through a lowpass filter, with one envelope shaping its brightness and another its volume. Every note opens bright and settles darker as you hold it. This is the architecture behind most classic monosynths, and the patch to learn first: once you understand it, most other patches are variations on it.

Load it: choose 📚 Examples → Basic Subtractive in the toolbar. Press ▶ Play, then play the Z to M keys. The patch file is patches/basic-subtractive.json.

Or play it here: press ▶ Play in the corner. The full app is a click away under Open in Soba. Two envelopes from one gate: one for the filter, one for the VCA.

What it teaches

  • Subtractive synthesis. Start with a waveform rich in harmonics and take some away with a filter.
  • Separate envelopes for tone and volume. Brightness and loudness can move on different schedules.
  • Filter CV in octaves. The envelope opens the filter by a musical interval, not a number of hertz.

Modules

ModuleSettings
Note InSource Keys, Voices 1, Key Vel 100%
OscillatorWave Saw
SVF FilterCutoff 700 Hz, Res 30%
ADSR Envelope (filter)Atk 1 ms, Dec 300 ms, Sus 30%, Rel 200 ms
ADSR Envelope (amp)Atk 5 ms, Dec 200 ms, Sus 70%, Rel 300 ms
VCALevel 54%
Audio OutputVol 80%

How it's built

The audio path

[Note In Pitch] ──> [Oscillator V/Oct]
[Oscillator Out] ──> [SVF Filter In]
[SVF Filter LowPass] ──> [VCA In]
[VCA Out] ──> [Audio Output Mono]

The saw wave contains every harmonic, so it's the richest raw material for a filter. The SVF's lowpass output keeps what's below the cutoff. At 700 Hz with a little resonance, the tone is warm, with a slight edge at the cutoff.

Two envelopes from one gate

[Note In Gate] ──> [ADSR (filter) Gate]
               ──> [ADSR (amp) Gate]
[ADSR (filter) Out] ──> [SVF Filter Cutoff]
[ADSR (amp) Out] ──> [VCA CV]

One output can feed any number of inputs, so Note In's gate starts both envelopes at once.

The amp envelope shapes the volume through the VCA. It rises in 5 ms, which is quick but not a click, falls to 70% over 200 ms, and fades out over 300 ms after you let go.

The filter envelope shapes the brightness. The SVF's Cutoff input works in octaves, and its CV Amt is at 1, so +1 doubles the cutoff. As the envelope jumps to its peak of 1.0, the filter opens one octave above the knob, to 1.4 kHz. Over the next 300 ms it settles to its 30% sustain, about 860 Hz. That fall in brightness, faster than the fall in volume, is what makes each note sound plucked rather than switched on.

Variations

Fatter bass. Replace the SVF with a Ladder Filter and use its LP24 output. Turn Oct on Note In down to −1, set the Ladder's Drive to about 2x, and lower its Cutoff to 300 Hz.

Acid squelch. Raise Res to 70% and lower Cutoff to 400 Hz. The filter envelope now sweeps a sharp resonant peak across each note.

Pluck. Set the amp envelope's Sus to 0% and Dec to 400 ms, so every note dies away even while held.

Supersaw. On the Oscillator, set Voices to 7 and Detune to about 40%. Seven detuned saws through the same filter make a wide, shimmering lead.

More sweep. Turn the filter's CV Amt up to open it by more than an octave: 2 takes the peak to 2.8 kHz, 3 to 5.6 kHz. Lower Cutoff as you go, so the notes still settle dark.

Space. Add a Stereo Delay and a Reverb between the VCA and the Audio Output.