Additive oscillator

Most oscillators hand you a finished waveform: you pick Saw, Square, Triangle, and the shape of the tone is decided for you. The Additive oscillator turns that around. Instead of choosing a ready-made wave, you build the tone up from its individual harmonics, one partial at a time, and see the whole harmonic spectrum laid out in front of you. Every waveform is really just a particular recipe of harmonics; Additive lets you write that recipe yourself.

That means direct control over the timbre at its source. Want a saw with the third harmonic pulled down and the seventh boosted? Draw it. Want only the first few partials for a soft, hollow tone? Draw that instead. Nothing is off-limits, because you are shaping the spectrum itself rather than reaching for the nearest preset shape.

Additive versus Wavetable

Additive and the Wavetable oscillator both give you more than a single fixed wave, but they get there in opposite ways:

Wavetable morphs through a set of pre-made waves. You sweep the Position control and the tone glides from one finished shape to the next. The waves already exist; you choose where along them to sit.
Additive lets you draw the harmonics live. There is no pre-made set to move through: the spectrum is exactly what you put there. You are building the wave, not selecting from a shelf of them.

Reach for Wavetable when you want to sweep between characterful shapes over time. Reach for Additive when you want to design one specific harmonic tone by hand.

Two tabs: Spectrum and Analog

The additive editor is split into two tabs. The Spectrum tab is where you draw the 32 bars and set the base shape, tilt, stretch, noise, partial groups, and the shaping tools: everything that decides the harmonic recipe itself. The Analog tab holds the parts that add movement and life over that recipe: the per-partial life controls (drift, variance, drive) and the per-group envelope faders.

Draw the tone on the Spectrum tab first, then move to the Analog tab to set it breathing.

The drawable spectrum

The heart of the Additive oscillator is a row of 32 harmonic bars. The left-most bar is the fundamental (the pitch you play); each bar to the right is the next harmonic up. The height of a bar is how much of that harmonic is present in the tone. Drag a bar up to bring that partial forward; drag it down to thin it out or silence it entirely.

Building a spectrum bar by bar from silence is possible, but you will usually start from a familiar shape and sculpt from there. The starting-point presets fill all 32 bars with a classic recipe in one click:

Saw: every harmonic present, falling off gently. Bright and full, the richest starting point.
Square: odd harmonics only, hollow and woody.
Triangle: odd harmonics again, but falling away much faster: softer and rounder than a square.
Sine: just the fundamental, nothing above it. The cleanest possible starting canvas.
Flat: every harmonic at equal height. Not a musical waveform on its own, but the most neutral base to draw on.

A preset is a starting point, not a lock. Once the bars are filled, draw on top of them freely: pick Saw, then pull down a couple of harmonics that feel harsh, or nudge one partial up to add a formant-like peak. The preset gets you in the neighbourhood; your drawing does the rest.

Tilt (brightness)

Adjusting 32 bars by hand is precise but slow when all you want is “a bit brighter” or “a bit darker”. Tilt does that in one move: it slopes the whole spectrum at once, lifting the high harmonics relative to the low ones (brighter) or the low relative to the high (darker), without you having to touch a single bar.

Tilt also keeps the tone full-bandwidth above the range you drew. The 32 bars cover the lower, most character-defining part of the spectrum; Tilt lets the tone stay open and airy above them rather than falling off a cliff at the last bar. In practice it is the fastest way to match the Additive oscillator’s overall brightness to the rest of a patch: draw the character you want in the bars, then use Tilt to seat it in the mix.

Stretch (inharmonicity)

A pure harmonic spectrum stacks every partial at a whole-number multiple of the fundamental: that exactness is what makes it read as a clean, in-tune “note”. Real instruments are rarely that tidy. A struck string or a bar leans its upper partials slightly sharp, and that gentle drift is a big part of why a piano sounds like a piano and a bell sounds like a bell.

Stretch lets you dial that drift in. At the centre the partials sit on the pure harmonic series, exactly as you drew them. Push it one way and the upper partials spread apart, sharpening as they climb: a little gives you the warm, slightly-detuned body of a struck string or a plucked piano note, and more takes you toward the clangy, metallic ring of a bell or a tuned bar. The lower you play and the further you push, the more pronounced the effect, just as it is on the real instruments.

Stretch is musical rather than technical: there is no formula to reason about, just a control you turn until the tone stops sounding like a synth and starts sounding struck.

Noise and texture

Harmonics alone are perfectly pitched, which is exactly why some sounds stay out of reach. Breath on a flute, the air in a pad, the scrape of a bow, the wash of a cymbal: none of those live on the harmonic series. They are noise, sitting alongside the pitched partials rather than replacing them.

The Noise layer adds that residual texture on top of your spectrum. Two controls shape it:

Level sets how much noise sits under the harmonics: off for a clean tone, a touch for breath and air, more for an overtly textured, hissy or scraped character.
Colour tilts the noise from dark to bright. Dark is a low, airy rush good for breath and body; bright is a fine, hiss-like top end that suits cymbal wash, brushed textures, and the edge of a bowed string.

A little noise is often the difference between a spectrum that sounds synthetic and one that sounds played. Set the pitched character in the bars, then use Level and Colour to seat some real-world texture around it.

Partial groups

Nudging 32 bars one at a time is precise, but sometimes you want to move a whole region of the spectrum at once: “bring the low end forward”, “thin out the top”, “lean on the odd harmonics”. Partial groups do exactly that. They divide the harmonics into a handful of bands and give you one level per band, so you sculpt the tone by region instead of partial by partial. It works like a small spectral EQ built right into the oscillator.

A Group Mode chooses how the harmonics are divided:

Octave bands: groups the partials into octave-wide ranges, low to high. The natural choice for broad “darker / brighter” shaping across the whole spectrum.
Odd / Even: splits the harmonics into the odd set and the even set. Lean toward odd for a hollow, reedy, square-ish character; lean toward even for a fuller, rounder tone.
Low / Mid / High: three broad regions, the body, the presence, and the air. Quick to grab when you just want to balance the tone in thirds.

Set a mode, then ride the per-band levels to shape the drawn spectrum by region. It is a fast way to rebalance a sound without redrawing it: pull the high band down to tame a harsh preset, push the odd band up to hollow a tone out, or lift the low band to add weight.

Each oscillator keeps its own group mode and band levels, and they save with the patch alongside the bars.

Each partial group’s level is also a modulation destination, so you can route an envelope or an LFO to a single group for spectral movement beyond the built-in group envelopes.

Group envelopes (evolving harmonics)

The bands above are static: set a level and the group holds it for the whole note. Group envelopes let those bands move instead. The group-envelope faders live on the Analog tab. Each of the groups can have its own gentle envelope that starts the band louder or quieter than its resting level and then eases back to it over a time you set, all while the note plays.

This is the difference between a spectrum that sits still and one that breathes. Start the high bands bright and let them settle, and a note opens with an airy attack that mellows the way a plucked or struck sound does. Give the higher bands shorter times than the lower ones and the top of the tone fades first, the natural motion of a real harmonic sound decaying. Push a band the other way and it swells in from below its resting level instead.

Depth (per band) sets how far above or below its resting level the band begins: positive starts it louder, negative starts it quieter, centre leaves it static.
Time (per band) sets how long that band takes to ease back to rest.

The ease back to rest carries a subtle analog snap: rather than settling in a straight, purely mathematical curve, it eases in with the slightly-overshooting character of a real hardware envelope, sharpening the knee of the movement without ever changing where the band finally lands. It is a small thing you feel more than hear, part of what keeps the movement from sounding mechanical.

Because each band has its own depth and time, several regions of the spectrum can be moving at once, in different directions and at different speeds, giving the tone a living, evolving character that a fixed spectrum cannot.

Analog character

A drawn spectrum is perfectly precise, and left completely still it can sound a little clinical, more computer than instrument. The analog character controls add the small imperfections that make a real oscillator feel alive, without disturbing the harmonics you drew. These controls live on the Analog tab.

Variance gives each harmonic a tiny, fixed detuning that is slightly different every time you play a note. The partials drift a hair apart from a perfect tuning, so stacked notes beat gently against one another and a chord shimmers instead of sitting dead still. It is the difference between a spectrum that sounds sampled and one that sounds played.
Drift keeps that movement going. Where Variance is a fixed offset for the life of a note, Drift lets each harmonic slowly wander in tuning as the note holds, the way a real analog oscillator is never quite still. A companion rate control sets how quickly that wander moves, from a slow, almost imperceptible float to a more obvious, restless motion.
Drive adds analog-style saturation and warmth to the whole tone. It runs the finished sound through a soft, tube-like saturation that thickens it and brings out extra harmonics from the ones you drew. A touch adds body and glue; more pushes toward an overtly warm, driven character.

All three sit at their off position by default, so the additive oscillator stays perfectly clean until you reach for them. Turn them up and the tone gains the movement, beating, and warmth of hardware while keeping the exact spectrum you designed.

Drive and Drift can be modulated. Both are available as destinations in the modulation matrix, so an LFO or an envelope can open the warmth or the wander up over the course of a note, breathing the analog character in and out rather than leaving it fixed.

Shaping tools

Four tools speed up the drawing itself:

Snap: constrains your drawing so bar heights land on clean steps rather than wherever the mouse happens to fall. Good for deliberate, tidy spectra and for matching harmonics to one another by eye.
Odd: keeps only the odd harmonics and clears the even ones, the recipe behind hollow, square-and-triangle-flavoured tones. A one-click way to move a spectrum toward that reedy character.
Normalize: rescales the whole spectrum so its loudest harmonic sits at the top of the range, without changing the balance between harmonics. Use it to bring a quiet, sculpted spectrum back up to full level after you have drawn it down.
Reset: clears your drawing back to a clean starting state, ready to begin again.

Working with the Additive oscillator

A few practical things worth knowing:

The 32 bars you draw define the character band, but the tone carries more harmonics than that above the range you draw, so it stays open and full rather than stopping dead at the last bar. Very high notes automatically shed their top harmonics as they climb, so the sound stays clean and never turns harsh no matter how high you play.

All three oscillators can be Additive, each with its own spectrum. You can run three independently drawn Additive tones at once, or mix one Additive oscillator against a Saw and a Wavetable. Each oscillator keeps its own set of 32 bars.
Your spectrum saves with the patch. The bars, tilt, stretch, noise, group mode and band levels, and the preset you land on are all stored with the preset, so a sound you draw today loads back exactly as you left it. Each oscillator keeps its own set.
Tune it like any other oscillator. The normal Octave, Coarse, and Detune controls work as they always do: shift it by octaves, tune it to an interval, or detune it slightly against another oscillator for beating and width.
Leaving Additive is just a type change. To go back to a fixed waveform or any other oscillator type, reselect it from the oscillator’s type menu, exactly as you would switch between Saw, Square, or Wavetable. Your drawn spectrum stays with the patch, so you can return to it later.