crocus.

1Quick start

The shortest path from "loaded the script" to "playing chords."

1. Pick a sound. On the norns, open PARAMS > crocus > voice. On first load crocus auto-selects something polyphonic; you can browse the list any time.
2. Hold a chord type, tap a root. On the grid, hold the maj pad (row 2, third from the left) with one finger. With the other hand, tap the C pad on the bottom row — you hear C major. Lift the chord-type pad and the chord stops.
3. Move the chord around. Keep maj held; tap any other bottom-row cell. You're shifting the root through the chromatic scale.
4. Add an extension. Still holding maj, tap an extension pad (row 4 or 5). Default behavior adds the new note without retriggering the chord; release the extension to drop it.
5. Latch instead. Tap the rightmost cell on row 6 — now the chord stays sounding after you release the root. Tap the same root again to stop.
6. Drum + arp. Top-right corner of the grid (row 1, col 16) starts the drum pattern. Row 2, col 16 turns the arpeggiator on.

2The norns + grid

crocus runs on monome norns. You drive most playing from the 16×8 grid; you change settings and watch state on the norns OLED with its three encoders (E1–E3) and three keys (K1–K3).

What the encoders + keys do

3Grid map

16 columns × 8 rows. The map below matches the physical grid as it sits in front of you with the USB cable pointing away: row 1 on top (drums + spicy chord qualities), row 8 on the bottom (root pads). Columns are 1 → 16, left to right.

How the rows behave

• R1 (top): spicy chord qualities (C1–C4) plus the drum cluster — beat division (C7/C8), beats volume (C10/C11), drum pattern (C13/C14), and beats run on/off (C16).
• R2: normal chord qualities (C1–C4) plus the arp cluster — arp rate (C10/C11), arp mode (C13/C14), arp on/off (C16).
• R3: bass cluster — bass dial (C10/C11), bass voice picker (C13/C14), bass on/off (C16).
• R4: normal extensions (C1–C4).
• R5: spicy extensions (C1–C4) plus the chord-tweak cluster — voicing± (C10/C11; pair-held resets the dial, or sets the split point in Split mode), octave± (C13/C14; pair-held resets), and the voicing-mode toggle (C16, Octave ↔ Split).
• R6: modes & cycles — play-style cycle ± (C10/C11; pair-held resets to Simple), perf-mode ± (C13/C14; pair-held resets to off), and the key-mode toggle (C16, snap on/off).
• R7: hold-mode toggle on C16 (strict ↔ latch); rest of the row reserved.
• Right-edge column (C16) is the toggles column: R1 beats run · R2 arp on/off · R3 bass on/off · R5 voicing mode · R6 key mode · R7 hold mode.
• R8 (bottom): chromatic root row. Every cell is a root pad; offset = col − 4 semitones added to the current key root. C4 is the anchor (offset 0). C1–C3 are left-anchor cells — they sound A, A♯, B in the octave below the C anchor (so the relative minor sits within reach). C16 (offset +12) is one octave above the anchor. Brightness shows scale membership when Key Mode is on.

Pair-hold gestures

Every cell marked with the orange underline is a ± pair: holding both cells of the pair simultaneously for ~1 second resets that one parameter to its param_spec default. Two pairs have additional special behavior:

• R3 C10 + R3 C11 (bass dial ±) held for ≥ 2 seconds fires Reset-to-defaults for every crocus param — the global escape hatch from a drifted session.
• R6 C10 + R6 C11 (voicing ±) held for ≥ 200 ms while voicing_mode = Split enters SET_SPLIT_MODE; the next R8 root-pad press writes that pad's column to voicing_split_index. In Octave mode the same gesture simply resets voicing_dial.

The bass-voice ± pair (R3 C13 + R3 C14) is also pair-hold-aware, but its pair-hold short-cuts to the "share with chord voice" nb-voice picker entry instead of a numeric reset.

4Playing chords

Hold Mode: Strict vs Latch

This is the single most important behavioral toggle.

• Strict (default): hold the chord-type pad while you tap a root — chord plays. Lift the chord-type pad → chord stops. This is the "play live with two hands" mode.
• Latch: tap the chord-type pad and a root — chord stays sounding. Tap the same root again to stop it. Lets you set a chord and walk away.

Toggle with row 6, column 16 (the rightmost cell on the master row), or via PARAMS.

Holding multiple roots (Strict only)

Hold two roots at once. The most recently pressed one is the active root — that's what sounds. Release it; the previous root is promoted and its chord resumes. Lets you "stack" chord changes in time without ever having a silent gap.

Play Style: Simple, Advanced, Free

5Chord types & extensions

Eight chord types

Two rows of four pads on the upper-left of the grid:

Eight extensions in two banks

Hold any combination — they stack. Examples: maj + m7 + 9 = C9, maj + m7 + ♯9 = C7♯9 (the Hendrix chord), min + m7 + 9 + ♭13 = Cm9♭13.

Add Note vs Play Chord

How the script reacts when you add an extension while a chord is already sounding:

• Add Note (default): plays the new extension's single note over the chord without retriggering. Releasing the extension drops just that note.
• Play Chord: full re-trigger of the chord with the new extension included. Release retriggers without it.

Set in PARAMS > Trigger > extension_addition or in the Options screen.

6Voicing

Two dials live next to each other on the Minilab faders 1 & 2 — Bass Voicing (Fader 1) sets bass octave; Chord Voicing (Fader 2) sets where the chord notes sit. Both are also reachable from the Bass and Home screens on the norns.

Chord voicing — the algorithm

Two algorithms ship; pick in Options > voicing_source.

• Orchid (default) — 0..60 step dial. Each integer maps to a specific position (Root / 1st inversion / 2nd inversion / spread). Default 20 = mid-register Root position. Verified note-for-note against Orchid's published Visualizer table.
• Crocus — ±4 step dial with chord-aware voice-leading. Smoother for songwriting; less predictable than the Orchid table.

Bass voicing

The Bass Voicing dial is bass_dial in PARAMS — an octave offset for the bass voice (±2 octaves). 0 places bass one octave below the chord root in the default Chords Only bass mode; +1 lifts it to chord-root octave; -1 drops it another octave. In Unison bass mode it follows the played pad's pitch class instead, with the same ±2 octave range.

Octave vs Split mode

• Octave (default): chord plays at its voiced position no matter which root cell you tap.
• Split: root cells beyond a configurable threshold play the chord +12 — like a piano split. Pair-hold the voicing± cells (row 6 cols 10/11) for 200ms in Split mode, then tap a root to set the threshold.

7Bass

Four bass modes, each with the bass voicing dial as a sub-modifier.

Pick a separate nb voice for bass at PARAMS > bass voice. Set "share with chord" if you want both through the same engine. Toggle bass on/off with K2 on the Bass screen.

8Performance modes

Choose how the chord articulates. Eight modes, all reachable from the Perform screen (E2 cycles).

Quantization

Options > quantization snaps Strum / Slop / Harp per-note timing to a grid: none, 1/32, 1/16, 1/8, 1/4, 1/16t, 1/8t. Pattern and Arp are already step-locked, so quantization doesn't apply to them.

Perf Lock

K3-long on most screens toggles perf_lock. With it on, changing the perf mode stages for the next press instead of interrupting the current performance.

9Scales & Key Mode

crocus understands three orthogonal pieces: a scale root (any of 12 pitch classes), a quality (Major or Minor), and a scale type within that quality. With Key Mode on, off-scale root presses snap to the nearest in-scale pitch.

Eleven scales

Setting the scale

Three places, all equivalent:

• Options — scroll to key_mode, key_root, key_quality, scale_mode (entries 4–7). Editing any of the last three auto-enables Key Mode.
• Quick-Key gesture — K2-long on Home or Key screen, then tap a root pad (hold the Min chord-type pad to set Minor). Sets root + quality + auto-enables Key Mode.
• PARAMS > crocus > Chord — same params, integer values; use Options for cleaner labels.

10Beats & tempo

Eight drum patterns ship: 4-on-floor, rock, half-time, breakbeat, samba, jazz brushes, dembow, kick + crash. Toggle on/off with the rightmost cell on grid row 1, or K2 on the BPM & Beats screen.

Set BPM (40–240) on the BPM screen with E2. Tap tempo: K3 on the BPM screen — each tap derives BPM from the rolling-window average interval (4 most recent taps; 0.2..3.0 sec valid). Time signature: K3-long cycles 4/4 → 3/4 → 6/8.

11FX

Three send-style effects on the engine output, all in PARAMS > crocus > Audio:

12Screens

E1 cycles eight views. Each shows what's relevant to the current task and re-purposes E2/E3/K2/K3 accordingly.

13MIDI & Minilab 3

MIDI input

Plug any MIDI controller into the norns. crocus listens for keyboard notes (root + octave + velocity) and CCs. Configure the device + channel in PARAMS > MIDI Input. With a velocity-sensitive keyboard you get full dynamic range; the grid sends a constant velocity.

MIDI clock + transport out

crocus sends MIDI Clock (24 PPQN) plus Start/Stop (0xFA / 0xFC) when enabled. PARAMS > MIDI Output > Clock Out defaults to OFF so external gear isn't surprised on first boot. Set the device + flip the toggle to drive an external sequencer in lock-step with crocus's BPM.

Minilab 3 layout

crocus has a built-in mapping for the Arturia Minilab 3 — the most common compact controller. Below is an approximate top-down of the physical hardware with each control's target. Faded cells are unmapped — they're free for you to bind via norns Settings > MIDI.

Reading the schematic: labels show physical control name → MIDI CC# (or note range) → crocus target. "Unmapped" = the CC arrives but crocus drops it; you can bind those CCs externally via norns Settings > MIDI without conflict. Two faders changed from the original ChordLab defaults: F3 was octave (now driven by face-value MIDI keyboard) and F4 was slop (moved to E2). F3 + F4 now drive the extension banks with curated 8-stop sweeps — see "Extension faders" below.

Device + channel

• MIDI In Device: norns vport 1..16. Pick the vport whose name matches your controller. Hot-plug is fine — vports are stable across reconnects.
• MIDI In Channel: omni by default. Set to 1..16 to filter.
• Pad Channel: default 10 (Arturia Minilab 3 factory). Pads use a separate channel from the keyboard; routing decisions check this channel.
• Pads → Chord Types: on/off toggle for pad routing. When off, pad notes fall through to keyboard handling.
• CC → Params: on/off toggle for CC mapping.
• MIDI Diagnostic Log: when on, prints every incoming MIDI event to the maiden REPL. Use to reverse-engineer your device's actual CC numbers (Arturia MCC presets vary) or to capture event streams for bug reports.

Keyboard notes → chord roots (face-value octave)

External keyboard notes drive the chord-engine root row exactly like a grid R8 press. The MIDI note's pitch class selects the root (pc = note % 12); the MIDI note's octave drives the crocus octave param so a 25-key controller (C2..C4) spans crocus octaves 2..4 instead of folding to one octave. Velocity carries through to the chord engine.

Pressing C4 (MIDI 60) plays Cmaj at octave 4. Pressing C2 (MIDI 36) plays Cmaj at octave 2. The on-screen octave param visibly updates to the played octave; this is intentional — the keyboard's Oct+/Oct- buttons therefore "just work" via the implicit MIDI-octave shift.

For chord triggering: same gating as grid R8 presses. In Simple play_style (default), chord plays only while a chord-type pad (grid OR Minilab pad — see below) is held.

Minilab 3 pads → chord types

The 8 pads in bank A send notes 36..43 on channel 10 (Arturia factory). Each pad maps to one of crocus's 8 chord types — single GRID_KEY_DOWN action, no extension side effects. Hold to gate chord (same semantics as grid chord-type pads).

For 7ths, 9ths, etc.: add extensions via the grid R4/R5 extension rows OR via PARAMS > Chord > extensions_normal / extensions_spicy. The Minilab pads stay focused on chord-type selection only — keeping the live-jam workflow simple.

Pads do exactly one thing — chord-type select. Toggle behaviors (arp on/off, beats run, hold mode, etc.) live on the grid and PARAMS menu, not on the Minilab pads.

CC → crocus params (Minilab 3 factory)

From the ChordLab brief at reference/orchid-clones/chordlab/PROJECT_BRIEF.md:

CC modes explained:

• Absolute: CC value 0..127 → linearly scaled into the target param's full range. Fader at top = param max.
• Relative-binary: Arturia detent encoders. CC value 64 = no change; 65..127 = +1..+63; 1..63 = -63..-1. Sends to SET_PARAM_DELTA.
• Press: action fires on rising edge (CC value > 0). Releases ignored.
• Threshold: binary param toggle. CC < 64 → low value; CC ≥ 64 → high value. Used for sustain-pedal-style switches.

Live-jam philosophy

The mapping deliberately covers the controls you'd touch during a performance — voicing, perf mode, strum, slop, bass, arp, hold, screen navigation, and live extension sweeps. Key/scale/transpose live in PARAMS or on dedicated screens (E2 on the Key screen for example) because those decisions are made before the jam, not during. Octave isn't on the encoder map either — face-value MIDI octave (the keyboard's own Oct± buttons or just playing different octaves) drives it for free.

Encoders 5..8 are explicitly left unmapped so you can bind them via norns' Settings > MIDI menu to whatever nb voice / audio params your current setup needs (filter cutoff, reverb send, sub osc level, etc.) — without those bindings fighting crocus.

Extension faders (Faders 3 & 4)

The two extension faders give live, between-press control over the chord's color tones. Fully down on a fader = no extensions in that bank; sliding up walks through 8 curated stops covering single extensions and common combos. Each stop is exactly 16 CC units wide.

Fader 3 → normal extensions (m7, M7, 9, 13 — per lib/kernel/harmony.lua):

Fader 4 → spicy extensions (b9, #9, #11, b13):

Both faders work together — sliding both to a non-zero stop combines normal + spicy bits on the next chord trigger. Combos beyond the curated stops (e.g. m7+M7) require setting bits manually via the grid R4/R5 extension pads or PARAMS > Chord.

On-screen preview: as you move either fader, the chord-name display on the Home screen updates live to show the chord name with the new extensions (e.g. "C" → "C9" → "C9♭13"). The currently-sounding chord doesn't retrigger — you're previewing the next press. Trigger a chord (chord-type pad held + root key) to hear the new color.

Unmapped / awaiting your CC capture

Minilab 3 buttons whose CC depends on your Arturia MCC config (default may vary):

• Octave +/-: the keyboard's built-in Oct+ / Oct- buttons typically SHIFT the keyboard's transmitted MIDI notes rather than sending a CC. Combined with crocus's face-value MIDI octave, this means Oct+ / Oct- already work — pressing Oct+ raises the keyboard's output by an octave, and crocus's octave param follows automatically. If your MCC config sends Oct buttons as CCs instead, enable Diagnostic Log to capture them and wire explicitly.
• Hold: TBD. Default behavior in Minilab 3 factory varies. Surface via Diagnostic Log; a natural target is cycling play_style (Simple → Advanced → Free).
• Transport buttons: Play / Stop / Record — depend on MCC. Use diagnostic capture, then I can wire to e.g. beats_running, RESET, Reset-to-defaults.

Quick start with the Minilab

1. Plug in. PARAMS > MIDI Input > MIDI In Device: pick the Minilab vport.
2. Hold pad 21 (maj). Play a note on the keyboard. Chord fires — C4 = Cmaj at octave 4, C2 = Cmaj at octave 2.
3. Release the pad. Chord stops.
4. Sweep Fader 1 for bass voicing, Fader 2 for chord voicing.
5. Sweep Faders 3 & 4 through their 8 curated extension stops; the chord-name display previews the next press live.
6. Turn Encoder 3 to cycle perf modes; Encoder 4 sets strum speed; Encoder 1 sets arp rate.

Grid optional from here.

14Quick-Key & Reset gestures

Quick-Key Select — change key in one gesture

1. K2-long on the Home or Key screen — the OLED prompts "Pick key."
2. Tap a root pad. Hold the Min chord-type pad while tapping if you want the key to be Minor.
3. Done. key_root_pc, key_quality, and key_mode = ON are written. The current scale type is preserved across the change.

If no pad is tapped within modal_auto_dismiss_sec (default 3 s), Quick-Key exits without changes.

Reset to defaults

Two ways to start over:

1. Pair-hold the bass dial cells (row 3, columns 10 + 11) for ≥ 2 seconds.
2. Options screen → "Reset to defaults" → K2 to confirm.

Resets every crocus param to its default. PSET files on disk are not touched.

15Mirrors & diverges from Orchid

One-screen comparison of where crocus follows the Orchid spec and where it walks its own road.