FOLIUM

Hello. This is the Folium manual, and really it’s just me walking you through the instrument the way I would if you were sitting next to me. Module by module, in the order you’ll actually want them. Read the first chapter with Folium open in front of you. Read the rest whenever a module makes you curious. You don’t need a theory background for any of it, and nothing you’ll want in the first hour is hiding in an appendix.

One idea holds the whole instrument together: Folium listens to its tuning. Most synths treat a scale as a pitch chart. Folium treats it as a material. Change the tuning and the oscillator offers up different harmonics, the filters resonate at different partials, the sequencer slides between different degrees. Everything after this is detail.

Each chapter ends with a controls table: every knob, slider, button, and label in that panel, its range, and what it does. Nothing on the surface is left out. A few controls are clickable labels rather than obvious buttons, and I’ve marked those.

One set of gestures, everywhere. Every slider, bar, and dial answers to the same hand. Drag to set, Shift-drag for fine control, double-click to reset to default, mouse-wheel to step. Where a control does something different, the chapter tells you.

0 · Setting up

0.1 Installation

macOS. Run the installer. It places the CLAP and VST3 in the system plugin folders. The first time you open Folium, it sets up a home for your presets and tunings:

~/Library/Audio/Presets/Petals/Folium/
├── Factory/    68 presets, mine
├── User/       your saves
└── Tunings/    .scl scale files

Windows. Run the installer, or copy the plugin files from the zip into your CLAP and VST3 folders. The preset home lives in %APPDATA%\Petals\Folium\.

Open your DAW, find Folium under Petals, and put it on a track.

0.2 The first ten minutes

Play a note. You’re hearing the init patch: one carrier, a little phase modulation, a touch of fold, a short reverb. It’s plain on purpose, so you can hear what your hands do.

Now three moves, in order. They’ll teach you the instrument faster than any diagram.

Move one. RATIO. In the PETAL OSCILLATOR panel, drag the RATIO slider slowly while holding a note. You’re changing the frequency relationship between the modulator and the carrier. Whole numbers sound related, like brass and bells. The spaces between them sound clangorous, inharmonic, sometimes wrong in a useful way. Notice the slider has tick marks. Those aren’t decoration. More on those in chapter 2.

Move two. FM and FOLD together. FM sets how hard the modulator bends the carrier. FOLD takes whatever comes out and folds it back on itself, west coast style. Each one alone is polite. Push both and the sound turns dense, metallic, physical. Pull both near zero and you have a sine. The entire personality of the oscillator lives inside these two inches of screen.

Move three. Hold a chord and raise WIDTH. It’s the bottom slider in the FX panel. The voices bloom outward across the stereo field, each note finding its own place, the reverb staying anchored in the center. This is per-voice placement, not a widener. At zero it’s exactly mono. At full it’s dramatic. Most patches want something in between.

That’s the sound of the instrument. Everything else in this manual either shapes it, moves it, or tunes it.

0.3 The layout

One screen, three columns. The only thing that pages is the center display, which has two faces: a garden of ratios, and off.

Signal flows roughly left to right. Modulation lives in the middle and reaches outward. If you can see a control, you can automate it.

Header. Across the very top: the preset bar (chapter 9), the tuning-source label in the INPUT header (chapter 2), the license chip (chapter 10), the petals mark at the left, which is also the theme switch (chapter 12), and the maker’s credit by Petals beside the title. Folium is the instrument. Petals is the maker.

1 · Petal oscillator

Here’s the heart of it. One carrier, one modulator, one folder, and they all talk to each other.

Start with WAVE. It’s one slider with three stops, and it sets the carrier itself. All the way left is a plain SINE, the classic FM carrier, exactly the wave Folium has always played. Every old patch of yours lands here and sounds the same. Nudge it to WARP and that sine gets pulled off center so it leans on its even harmonics, like a wave drawn by hand instead of by a formula. A little warmer, a little fatter. Then the one I’m proudest of, all the way right: CARRIER. Here the wave gets rebuilt out of your scale. It’s a stack of partials and every single one is a degree of the tuning you loaded, so the wave’s own harmonics are your scale’s intervals. Load a different tuning and the wave itself changes underneath you. It’s gorgeous for drones and soundscapes that come straight out of whatever scale you’re in.

COLOR is brightness within whatever wave you picked. On WARP it leans the symmetry further. On CARRIER it sweeps from a near-sine at the bottom up to the full scale-degree stack at the top. On plain SINE there’s nothing to color, so it sits still. COLOR is a modulation destination like anything else, so point ENV 2 at it and the wave brightens with every note you play, the way hitting a string harder makes it ring brighter.

Now the two that carry most of the character. RATIO is the modulator’s frequency as a multiple of the carrier’s, anywhere from 0.5 to 16. This is the single most important control on the instrument. Simple ratios (1, 2, 3, 1.5) sound harmonic and pitched, like brass and bells. The messy numbers in between throw off sidebands that don’t line up with the note, and that reads as metal, glass, breath. This is also where the tuning comes back in: every ratio in your scale can be assigned to the RATIO slider, and then you slide right to it. More on that in chapter 2. FM is how hard the modulator bends the carrier. Zero is a pure carrier. A little adds motion and body. A lot piles on sidebands until the pitch dissolves into texture.

1.1 The wavefolder

Its own panel, right under the oscillator. Three knobs, and this is the west coast half of the sound.

FOLD is the amount, from clean at 1 up to fully folded at 8. Folding adds harmonics by reflecting the wave back on itself, and unlike a filter it adds where there was nothing. Even 1.5 changes the character. Four and up is an instrument all on its own.

BIAS is the symmetry of the fold. Dead center, the folder is symmetric and gives you only odd harmonics, hollow and clarinet-like. Push it off center and the even harmonics come in, fuller and fatter and more vocal. It stays in tune the whole time, so the new harmonics still belong to the note. That’s the classic west coast fattening move, done in your scale.

TYPE is the shape of the fold itself, one continuous knob that sweeps across three classic folders. Left is the clean sine fold Folium started with, blooming evenly as you push (the Buchla way). In the middle it saturates instead of multiplying, so even hard folding stays round and gentle (the Serge way). Right is a diode edge, harder and brighter with more bite (the Lockhart way). Because the knob is continuous, the spots between those three are folders nobody ever built in hardware. The name up in the Wavefolder header tells you where you are, and clicking it snaps to the next character.

One thing ties the whole panel together. Under RATIO, FM, and COLOR you’ll find mod bars: drag the ends to set how far a modulator sweeps, then click the little source label to pick LFO 1, LFO 2, ENV 1, or ENV 2. The moving dot on the bar is the modulator, live, showing you exactly where it is in its travel. FOLD and BIAS carry the same idea as a small satellite knob beside each. TYPE is the one that stands alone, no modulation. Full detail on all of it in chapter 5.

PETAL OSCILLATOR

WAVEFOLDER

The RATIO ticks show 1 · 1.41 · 3.5 · 7 · 11 with no tuning loaded, and your garden ratios once you load one. Unlocked, RATIO snaps softly to the ticks. Locked, it hard-steps between them. FM snaps softly too. The FOLD ticks are just guides.

Try. The ratio garden, end to end. Pick a tuning from the Input header (chapter 2). petals_kora.scl is a good first one: seven notes, easy to play with. Switch the center display to RATIOS and it lights up with the scale’s intervals. Click a few dots; each one becomes a step on the oscillator’s RATIO slider. Now click the Ratio label to turn on snapping, and drag the slider: it lands only on the intervals you picked. Set it to something other than 1:1 and bring FM up. That’s the whole idea in four moves.

Try. The folder, then the envelope. Keep that sound going and push FOLD up. Sweep TYPE through its three characters and hear the fold change shape; nudge BIAS off center for the fuller, even-harmonic side. Point a mod bar at FOLD or BIAS to set it moving. Then the envelope (chapter 4) shapes all of it over the life of each note.

2 · Tuning

This is the chapter that’s the whole reason Folium exists. Take it slowly, with a cup of something.

2.1 Sources

Folium takes its tuning from one of three places, in strict order:

1. An MTS-ESP master anywhere in your session. If one is connected, it wins, always, and Folium follows it live, including retuning while notes are sounding. While a master is connected the tuning menu is locked: the master is authoritative.
2. A Scala file. Click the tuning label in the INPUT panel header (it reads 12-TET until you change it) and choose any .scl file from your Tunings folder. No other software required. Drop new files in the folder; Folium rescans it every time you open the plugin window, so a new scale shows up the next time you open the editor.
3. 12-tone equal temperament, when nothing else is loaded. The familiar default.

The label always tells you which source is active. Patches you save remember their scale. Load one on a machine with no tuning software and it still plays in tune with itself.

2.2 The garden

Switch the center display to RATIOS. Every dot is an interval from the current scale, laid out from the center outward: simple ratios near the middle, wider intervals toward the edge. Click dots to select up to eight. These become your ratios: the tick marks on the oscillator’s RATIO slider, and the grid the next two features snap to.

The garden needs a scale to draw. With an MTS-ESP master connected or a .scl file loaded, it blooms. On plain 12-TET with nothing loaded there’s no scale to show, so RATIOS reads a No Tuning Source standby. Load a tuning and the dots appear.

Selections are remembered by scale degree, not by frequency. Save a patch with degrees one, four, and seven selected, load any other scale, and the same degrees light up, now holding that scale’s intervals. Your harmonic choices travel with you. You can always select at least one and at most eight; the header counts them.

2.3 Ratio lock

The small lock on the RATIO label. Engaged, the slider snaps to your selected garden ratios. The oscillator can only land on intervals from your scale. Now sweep RATIO: it steps through pure, related timbres, one shelf at a time. Let an LFO or a MOTION lane drive RATIO while locked and you have melodic timbre sequences that cannot leave the scale.

2.4 Scale morphing

If your MTS master can morph between tunings (most can), do it while holding a chord with ratio lock on. The locked ratios glide to their new positions: short distances arrive quickly, long leaps take longer, each voice traveling on its own schedule. The garden re-blooms in real time as the dots drift to their new positions. No controls to set. It follows.

TUNING / GARDEN

Selection is keyed by scale degree, so it survives a tuning change. You can hold anywhere from one dot to eight. The dim outer dots are the same degree one octave (or period) up.

Try. Load petals_kora.scl from the Tunings folder. Open the garden. Select the unison, the fifth-ish dot near the center, and one outer dot that looks lonely. Lock the ratio. Sweep. That’s your scale, audible as timbre.

3 · Filters

Two state-variable filters wired in series, and each one has the four modes you’d expect: lowpass, highpass, bandpass, notch. Each also has its own drive and its own key tracking.

CUT sets where the filter works and RES sets how much it sings about it. It stays clean and stable across the whole range, and resonance emphasizes without ever screaming. Push RES toward the top and the filter starts to sing outright. DRIVE is a gentle even-harmonic saturation after each filter, the warmth of tape rather than the bark of a fuzz, and with two filters in series the two stages add up. KEY is continuous key tracking from zero to full; at full the filter opens as you play higher, so brightness stays even across the keyboard. Each cutoff also has its own mod knob and source cycle, exactly like the oscillator’s mod bars: dial in a depth, then pick LFO 1, LFO 2, ENV 1, or ENV 2.

3.1 The lock: scale resonance

This is my favorite trick in the whole instrument, and I haven’t found it in another synth, so read it slowly. Each filter has its own lock, the small petals mark to the left of the cutoff knob. It sits dim until you click it, then it lights murasaki.

Locked, the cutoff snaps to the harmonics of whatever notes you’re playing, chosen from your garden ratios, per voice. Now turn the resonance up past two-thirds or so and the filter stops being a tone control and becomes a resonator tuned to your music. Every note you play, the peak finds a partial of that note that belongs to your scale. Play a chord and each voice gets its own tuned emphasis. Sweep CUT while it’s locked, or let an envelope or LFO move it, and the filter steps from partial to partial, always landing on your scale, never sliding through the cracks between them. Crank RES until it sings and you can hear it plainly.

And because there are two of them, set both filters to self-resonate on the same scale, move them with LFOs or just by hand, and Folium turns into a dual resonator. You get these gorgeous stacked harmonic resonances that come entirely out of your tuning.

Key tracking is ignored while the lock is on, because the lock is tracking, quantized to your scale.

FILTER A and FILTER B (identical set, two blocks in series)

Order is fixed A → B in series. The lock is a cutoff lock; raise RES to hear it as a resonator.

Try. Filter A: lowpass, RES at two-thirds, lock on. Garden: a few simple ratios selected. Play slow single notes and sweep CUT gently. The filter sings along, stepping through the partials of your tuning. It’s my favorite trick in the instrument.

4 · Envelope, voices, glide

The envelope is one continuous curve, not a row of bars. The silhouette runs left to right through every stage: Delay, Attack, Hold, Decay, Sustain, Release. A bright playhead rides the line in real time as notes play, so you actually watch the shape move. It shapes loudness per voice, but because the wavefolder sits upstream it shapes brightness too, the way striking a real instrument harder makes it brighter.

You edit it by hand, right on the line. Drag a stage node to set its time and level. Grab the midpoint of any curved segment and pull, and that’s the bow handle: it bends the segment from linear toward exponential or logarithmic. Attack, Decay, and Release each have their own bow. The DAHDSR readout under the line mirrors every value as you drag (Dly, A, Hold, D, S, R), and the curve readout shows the three bends as signed percent.

There are two of these. ENV 1 is the amp envelope, always wired to loudness. ENV 2 is mod-only and completely free: it drives nothing until you point a mod destination at it. Both share one display, and the env1 · env2 cycle in the header picks which one you’re editing. To put ENV 2 to work, choose it as the source under any oscillator or filter destination (it’s the fourth choice after LFO 1, LFO 2, ENV 1), and its header shows you where it’s routed.

Each envelope rides its own lit dot down the line as a voice plays, so you can watch ENV 1 and ENV 2 move at once. The dot trails all the way through Sustain and Release, not just the attack, and in loop mode it traces the repeating orbit so you can read the rate by eye. Faint ghost lines preview what Key Track and Velocity will do before you even touch a note: raise kt and a second silhouette shows how the high register will compress, and the velocity ghost shows where harder playing is headed.

The line is a full DAHDSR. DELAY holds at silence before the attack starts, and HOLD holds at the peak before the decay begins. Both reach 2 seconds and both sit at zero by default, so straight out of the box the line is a plain ADSR.

Each envelope can also run on the grid. Flip its free · sync toggle to sync and the time stages stop counting in seconds and start counting in your DAW’s tempo: Delay, Attack, Hold, Decay, and Release each swap from a time to a musical division, anywhere from 1/32 up to 8 bars, dragged the same way as the sequencer’s offset and defaulting to 1/4. Drop a 1/16 attack, a 1/4 decay, a one-bar release, and the whole shape locks to the song; change the tempo and it follows. Sustain never syncs, because it’s a level, not a time. ENV 1 and ENV 2 sync on their own, so you can pin the mod envelope to the grid while the amp envelope breathes in free time, or the other way around.

A few more per-note touches. KEY TRACK (kt) scales the envelope times by pitch, signed from −100% to +100%: positive makes high notes faster, the way a real instrument’s top end decays quicker, negative flips it. The TRIGGER MODE label under the line cycles gate, one-shot, and loop. Gate is the normal one: hold the note and it sustains, let go and it releases. One-shot ignores note-off and runs the whole shape to the end. Loop repeats Attack into Decay over and over, fast or slow, which on ENV 2 turns the mod envelope into a third LFO. VEL sets how much velocity drives timbre: drag it up from zero and harder playing pushes the sound brighter and more folded.

Over in the INPUT panel, under the tuning label, VOICE MODE gives you three buttons. POLY is up to 8 voices, MONO retriggers on every note, LEGATO lets held lines glide without retriggering. Under those buttons is a strip of eight dots, the VOICE COUNT: click a dot or drag across the strip to set how many voices Folium stacks, one through eight. The filled dots show the count at a glance. Fewer voices steal earlier, which feels tighter and more deliberate; drop it to one and you’ve got a single voice that always retriggers. Eight is full polyphony.

GLIDE is portamento for mono and legato, up to half a second, and it has two personalities with the Glide label as the switch. Step, the default, moves pitch in small consonant increments, an audible staircase rather than a smear. Slide is the classic smooth portamento, an even exponential ease into the new note. Click the label to swap; it lights when Slide is on. Same knob, two characters. And OCT and BEND are octave transpose and pitch-bend range. Under a microtonal scale the octave button transposes by the scale’s own period, so an “octave” in a 31-note tuning moves 31 degrees, and the bend wheel bends in frequency, so the tuning keeps its character even mid-bend.

INPUT · ENVELOPE

ENV 1 is the amp envelope. ENV 2 is mod-only; route it from any destination’s source cycle (LFO 1 · LFO 2 · ENV 1 · ENV 2). Both carry the full DAHDSR set above, their own playhead, and their own free/sync toggle. SYNC locks the time stages to DAW tempo; Sustain stays a level and never syncs.

5 · Bloomscope

The display up at the top center is the front panel for the two LFOs, and its header is a two-way tab: RATIOS shows the garden of your scale (chapter 2), OFF is just a still mark.

Each LFO gives you ten shapes, and I named them for what they feel like rather than what they’d look like on a scope. They’re botanical on purpose. Cycle them with the chevrons or drag the name. Audition them for a minute and the names start to make sense.

• Bloom. A plain sine. The calm one. Smooth open and close, no edges. Start here.
• Spiral. A sine stretched by the golden ratio, so it never quite repeats where you expect. Restless, organic, slightly off the grid.
• Pulse. A soft-edged square. On, off, with the corners rounded so it doesn’t click. Gating without the hard edge.
• Scatter. Smoothed sample-and-hold. Eight random levels per cycle, curved between, so it lurches and settles like wind through leaves. Same seed every cycle, so it’s repeatable, not noise.
• Breathe. Asymmetric. Slow rise, fast fall. Seven-tenths of the cycle filling up, three-tenths letting go. A long inhale and a quick release. The most lifelike of the set.
• Petal. A rose curve, the absolute of a tripled sine. Three identical humps per cycle, each blooming up from zero and back. Rhythmic, repeating, flower-like.
• Orbit. Elliptical speed. It lingers at the extremes and rushes through the middle, the way a planet hurries at perihelion. Slow, fast, slow, weighted toward the edges.
• Tide. Two sines beating against each other at an irrational ratio (the square root of two). They drift in and out of phase forever, swelling and thinning. Never the same twice.
• Fern. A triangle raised to the 2.5 power. A sharp spike that eases off into a long curved tail. Snaps up, unfurls down.
• Corona. Quiet, with four bright gaussian flares per cycle. Mostly dark, then a sudden bloom of light, four times around. Sparse and dramatic.

RATE runs free in hertz (0.05 to 20 Hz) or syncs to the host tempo, from 8 bars down to a 16th-triplet, triplets included. SLEW smooths any shape’s edges when it’s set to Smooth, or leave it stepped. Each LFO has an on/off toggle on its label, and the MODE button flips it between Free and Sync.

Routing is simple, with one degree of freedom. Seven destinations come with a source already on them: LFO 1 holds RATIO, FM, COLOR, and CUT A; LFO 2 holds FOLD, BIAS, and CUT B. Most depths start at zero, so nothing moves until you open a lane. The init patch opens two of them, a little LFO 2 into FOLD and a little LFO 1 into CUT A, and that’s the gentle breathing you hear on the first note. The source under each destination is a cycle button (LFO 1, LFO 2, ENV 1, ENV 2), so any destination can follow either LFO or either envelope instead. ENV 2 is the mod-only envelope from chapter 4, and pointing a destination at it is how you put it to work. Under each destination sits a mod bar: drag its ends to set the range the source sweeps, and watch the moving dot, which is the modulator live, exactly where it is in its travel. The control keeps working while it’s modulated; the source just breathes around wherever you set it.

BLOOMSCOPE · LFO 1 · LFO 2 (each LFO identical)

Sync divisions (12): 8 bar · 4 bar · 2 bar · 1 bar · 1/2 · 1/4 · 1/8 · 1/16 · 1/32 · 1/4T · 1/8T · 1/16T. Destinations: RATIO, FM, COLOR, FOLD, BIAS (chapter 1) · CUT A, CUT B (chapter 3). Each destination’s source cycles LFO 1 / LFO 2 / ENV 1 / ENV 2.

6 · MOTION

Two lanes of eight steps each. They’re motion lanes, not note sequencers, and that one difference changes how you write them. I kept them deliberately small and simple, eight steps and no more, so you can get a groove going fast instead of getting lost in options.

A step sitting on the center line means “leave the control alone.” Above center pushes the parameter up, below pulls it down. The pattern is a deviation from wherever your hands already have things, not a replacement for them, so if you turn the control while the lane runs the whole pattern rides along with you. Drag a step and a readout shows you the deviation, signed, live.

Lane one moves RATIO. Lane two is assignable: FM, Fold, either filter cutoff, or Morph, which drives the A/B crossfader so a single lane can move the whole patch at once.

6.1 Writing patterns

• Drag a step to set it.
• Double-click a step to rest it. The lane goes quiet there. Double-click again to bring it back.
• Shift-click a step to tie it to the next. Shift-drag paints ties across a run.
• Drag the lane’s right edge to change its length, 1 to 8 steps.

6.2 Ties

A tied step doesn’t jump to the next value. It glides there, across exactly one step, the way a 303 slides between notes. Tied steps merge under a slur arc, straight out of notation. Chain ties for long multi-step glides. Tie the last step and the glide wraps across the loop point back into step one. The classic acid move. Glide into a rest and the motion settles before the silence: a phrase ending.

And my favorite combination: ratio lane + ratio lock + ties. The lane offsets RATIO, the lock snaps it to your garden degrees, the ties slide between them. The slur arcs turn sage to tell you it’s happening. You are now playing 303 lines in just intonation, or any scale you can imagine, with timbre instead of pitch.

6.3 Clocking

The TIME row reads like a sentence. The verb word switches the lane between autonomous (it runs its own clock) and played (notes drive it). Autonomous splits into Free (its own rate in hertz) or Sync (host divisions, dotted and triplet included). Played splits into Trig (advance on any note you play) and Note (advance only on a fixed trigger key: C5 for lane one, C#5 for lane two). An OFFSET delays a lane’s start by a musical amount, so two lanes can chase each other.

6.4 The ratio lane’s FINE panel

Lane one has a hidden FINE panel. Double-click the “MOTION 1” label to open it. It holds two toggles that change how the ratio lane reads, and they only exist here because the ratio lane is special. Lane two has nothing to expose, so its FINE row stays hidden.

SNAP quantizes the lane’s steps to your garden ratios. With SNAP on, the lane stops drawing a free continuous pattern and re-draws as rank bands: one evenly-spaced horizontal row per selected garden ratio, lowest ratio at the floor, climbing in scale order. Each band wears its garden dot’s color, so a step’s row tells you which interval it lands on at a glance. Drag a step and it lands on a whole band, never between two. This is what turns the lane into a pitch-true timbre sequencer. Every step is a degree of your scale.

BIPOLAR · ABSOLUTE sets what a step’s value means.

• BIPOLAR (default). Each step is a deviation from the RATIO slider. Center is “leave it”; up and down push its ratio further or nearer. Move the slider and the whole pattern rides along. This is the relative behavior the rest of the module uses.
• ABSOLUTE. The step is the ratio. The lane owns the oscillator’s ratio outright and the RATIO slider steps aside. Pair this with SNAP and the lane writes a melody in scale degrees, no hand in the loop. Bipolar leans the timbre. Absolute plays it.

The section header carries Clear and Random for the selected lane.

MOTION

Steps: drag = set · 2×click = rest · ⇧click = tie · ⇧drag = paint ties · drag right edge = length. Sync divisions (19): 1/32 1/32D 1/32T 1/16 1/16D 1/16T 1/8 1/8D 1/8T 1/4 1/4D 1/4T 1/2 1/2D 1/2T 1 2 4 8 bar. Offsets (11): OFF 1/16 1/8T 1/16D 1/8 1/8D 1/4 1/4D 1/2 1 bar 2 bar. Under a morph (chapter 8): step values crossfade continuously, ties flip at the fader midpoint, free rate glides; run mode and sync division hold where you set them. No reverse, no swing. The Note trigger key is fixed (C5 / C#5), not user-set.

Try. Lane one on, locked ratio, four steps up and down, shift-drag across steps two and three, tie the last step. Hold one bass note. You wrote a bassline without writing notes.

7 · FX and output

Five slider rows, top to bottom, in signal order. These effects lean toward texture and space more than anything showy.

NOISE is an always-there tape hiss, filtered dark. A little of it makes everything sit together, like the room tone of the patch. It’s quiet on purpose.

SPACE is the reverb decay, from a tenth of a second up to thirty. And this reverb is a little different: it’s an eight-line modulated network where each voice gets its own tail, so your whole sound isn’t crammed through one shared reverb. Each voice blooms in its own space and they sum together, which keeps the whole thing clean even when you’re holding a big chord. It blooms rather than rings.

TONE is the reverb’s damping: left is dark felt, right is glass. MIX is dry to wet.

WIDTH is the per-voice stereo placement from chapter zero. The voices fan out to fixed positions scaled by the slider, and the wider ones sit a touch quieter and drier, which your ear reads as depth. The image stays balanced at every setting, and mono playback is always safe.

Below the sliders is the voice meter, a thin helix of eight dots, one per voice. A silent voice is invisible; as a voice gets louder its dot warms from violet to rose, so you can read your polyphony at a glance and see exactly which voices are still ringing.

Under that is the output: a stereo level meter with the GAIN fader built right into it (drag the meter), plus the limiter LED, which lights when the master limiter is catching peaks. The limiter is always on as a safety, and there’s no threshold to set.

FX · OUTPUT

The level meter shows peak + RMS per channel; the peak marker reddens above −1 dBFS. The reverb keeps a fixed 20 ms pre-delay, and there’s no control for it.

Try. SPACE near 8 s, MIX around a third, TONE dark. Hold a low chord and let go. The reverb keeps blooming after the note. Now watch the voice meter while you play a fast run: you can see the voices being reused.

8 · Morph

The two buttons and the long slider at the bottom right. Press A and Folium captures everything: every knob, every mode, the lanes, the levels. Change whatever you like, then press B. Now the crossfader morphs between the two complete states, giving you both patches and every patch in between on one control, automatable straight from your DAW. And here’s the fun part: leave the fader on A and keep editing and it saves back into A, slide to B and edit and it saves into B, so with the crossfader automated in a performance you can keep tweaking mid-flight and get some genuinely wild motion out of it. The MOTION lane’s Morph target drives this same crossfader, so a lane can play patches the way the other lanes play parameters.

Three kinds of travel, so the morph always sounds intentional:

• Continuous values glide. Cutoffs, FM, fold, the envelope’s Attack/Decay/Sustain/Release, reverb, the MOTION lane patterns themselves: all of it sweeps from A to B. The sequencer’s free rate glides too. (Delay and Hold are the exception: they hold where you set them, never morph.)
• Switches flip at the halfway point. Filter modes, octave, LFO shapes, mod sources, trigger modes, envelope sync settings. Things that can only be one or the other change lanes at the midpoint, without a click.
• Your hands stay in charge of the anchors. Ratio lock, the filter locks, the sequencer’s run mode and sync division, and the voice setup don’t ride the fader at all. They stay exactly where you set them, through any sweep. Locks are commitments, not parameters.

Edit anything mid-morph and the edit lands in whichever snapshot is closer (A below halfway, B above), so the next sweep keeps your change. What you hear is always what the fader says.

MORPH

Glides: all continuous values, lane patterns, seq free rate. Flips at midpoint: filter modes, octave, bend range, LFO shape/slew/mode, mod sources, trigger modes, env sync + divisions, lane ties. Stays put: ratio lock, filter locks, seq run mode + sync division, voice mode + count. Env Delay/Hold never morph; they hold where you set them. Needs both A and B captured.

Try. Capture A on a soft sine pad: low FOLD, slow attack. Push FOLD and FM hard, shorten the attack, capture B. Now assign MOTION lane two to Morph and write a slow pattern. The lane plays the synth between its two selves.

9 · Presets

The bar across the top. The arrows step through patches, the name opens the browser, and SAVE does what it says. Factory presets save as copies into your User folder, and your patch name picks up an asterisk the moment it has unsaved changes; the dirty flag watches everything, lanes and locks included. (In demo mode, saving asks you to activate first, which is chapter 10.)

A preset is a .petal file, just readable JSON holding every parameter, both morph snapshots, the MOTION lanes, your garden selection by degree, and the tuning itself. Export and Import in the browser move patches between machines as single files, so a patch made in a 22-note scale arrives with its scale tucked inside.

The browser groups Factory and User in collapsible sections; the arrow keys move the focus and Enter loads. Open folder reveals the presets on disk. There’s no search field, so use folders to keep patches organized.

PRESET BAR · BROWSER

In the browser: load (click a row), Save, Save As, Init, Delete (User only, confirm twice), Import (.petal), Export (.petal), Open folder, collapse sections, and ↑/↓ + Enter.

10 · Demo and license

Folium is a free download, and the demo is the whole instrument. Every voice, every module, every tuning, nothing held back and nothing hidden. Two things mark it as a demo: every thirty seconds a soft wash of noise drifts through the output for a few seconds and fades away again, and saving or exporting patches is off. The chip in the header reads DEMO.

A license removes both, permanently. Buy Folium at petals.fm and your key arrives by email: a short block of letters and numbers. Click the DEMO chip, paste the key, and you’re done. Verification happens entirely on your machine, offline. No account, no server, no phoning home, ever. Your key works forever, on every machine you make music on.

Once activated, the header chip changes from DEMO to registered to . Click it to open the registration panel: the Petals mark, your name, and your email. If you bought without giving a name, your email stands in as the registered identity.

LICENSE

Lost your key? It’s in your purchase email. Otherwise: shades@petals.fm

11 · In the studio

State. Everything saves with your DAW project: every parameter, the UI’s entire arrangement, the tuning. Close the window, reopen it days later, and it’s exactly as you left it.

Window sizing. The panel fills whatever window you give it, no gap at any size. Recording your screen and want the grid dead crisp? Press Ctrl+Shift+S to snap the size to an exact, pixel-perfect step. Press it again to return to smooth fill. The setting sticks.

Switching patches while you play. Load a preset with notes held and the held notes change to the new sound without a click. No pitch swooping between patches, no stray glides. The same is true when a project reloads.

Automation. Every parameter is exposed to the host. Type values directly into automation lanes (“35%”, “2.5 kHz”, “B”) and Folium parses them. Discrete parameters (filter modes, voice count) show their full range.

Latency. The always-on true-peak limiter looks a little ahead, and Folium reports that lookahead to your DAW as plugin latency. Your host compensates, so recordings stay time-aligned.

MIDI. Sensible CC defaults out of the box: CC 74 to CUT A, CC 71 to RES A, CC 73 to attack, CC 72 to release. The sustain pedal (CC 64) holds notes the usual way. Pitch bend range is on the panel. CC 120 is the panic button (all sound off), CC 123 releases held notes.

Tunings on stage. No MTS master in your live rig? Put your scales in the Tunings folder and switch them from the Input header between songs. Patches carry their own as backup.

12 · Reference

Themes. The petals mark in the header cycles Petals at Night (the dark one you’ve been looking at) and Amiga 500, a warm light palette for bright rooms.

The folders. Presets and tunings live in plain folders (paths in chapter zero). Back them up like any other work. The browser’s folder button opens them.

When something seems wrong. One screen means no hidden state: if it sounds different, something visible is different. Check the locks, the lanes, the tuning label, the morph position. Stuck note? CC 120. Tuning label says a master is connected and you don’t expect one? Some plugin in your session is running MTS-ESP.

Word to the wise. The limiter at the end of the chain is a soft safety, not a mixing tool. The LED tells you when it’s working. If it’s always on, pull GAIN down and let the sound breathe.

Folium is made by Petals. Questions, patches you’re proud of, scales I should hear: shades@petals.fm