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@maru shared this instrument so you can build on it and use it in your DAW.

AvailableInstrument

OSC Mini

A compact subtractive synth for learning the signal path.

About

A compact subtractive synth: one oscillator into a resonant low-pass filter into an amplitude envelope. It is the classic signal path with nothing bolted on, small enough to learn in an afternoon and good for basses, plucks, leads and simple pads.

Controls

  • Wave picks the oscillator: sine, saw, square or triangle. Saw is the brightest and the usual starting point. A sine has no harmonics for the filter to remove, so the filter barely changes it.
  • Octave and Detune set the pitch: whole octaves up or down by two, and a fine offset of up to a semitone either way.
  • Cutoff is the main tone control: where the low-pass filter starts removing brightness. The mod wheel moves it by default.
  • Resonance adds a peak at the cutoff, from smooth to sharp and vocal.
  • Env Amt lets the envelope move the cutoff up or down with each note, for plucks that open and close.
  • Attack, Decay, Sustain and Release shape each note's volume. You can also drag the envelope curve directly.
  • Gain sets the output level. CC 7, the usual volume controller, moves it by default.

Voices and glide

OSC Mini starts monophonic, one note at a time. The voice settings switch it to eight-voice polyphony or to Mono Legato for connected lines, choose which held note wins in mono (the last, lowest or highest), and add portamento: a glide between notes of up to two seconds, either always or only when notes overlap.

Getting started

Play OSC Mini from a keyboard or a MIDI clip. Start with the saw wave, pull Cutoff down and raise Resonance a little for a bass. Shorten Decay with Sustain at zero and add some Env Amt for a pluck, or slow the Attack and Release for a pad in polyphonic mode.

In hosts that support patching, OSC Mini also appears as a Eurorack-style panel with a MIDI input and an audio output jack.

How it works.

The path is oscillator into a biquad low-pass into an ADSR into a gain stage, in that order, one voice at a time. The oscillator produces a band-limited waveform at the note frequency, offset by Octave and Detune. That signal runs through a second-order biquad low-pass, whose corner frequency is set by Cutoff and pushed around by Env Amt. The amplitude envelope then shapes level over the life of the note, and Master Gain scales what leaves.

The envelope is doing double duty: the same ADSR that controls loudness also modulates the filter cutoff by Env Amt. That's a deliberate simplification - real synths give the filter its own envelope, and if you want that, the clone-and-edit path below is about twenty lines of work. Sharing one envelope is why OSC Mini has eleven parameters instead of eighteen, and why the whole thing fits on one screen.

Two honest limitations. It is monophonic - new notes steal the voice, so legato playing retriggers rather than layers. And the filter is a single biquad, so it rolls off at 12 dB per octave and self-oscillates in the whistling-resonance way rather than the warm-analog way. Neither is a bug we plan to hide; both are on the list for OSC-1.

What would you make with OSC Mini?

Describe what you want to make. Build it with the Studio agent.

Goes well with.

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