Sonata (n.): a complete musical form — theme, development, resolution.
Sonata is a 28-key split keyboard layout. It is the minimalist variant of Cadence, sharing Cadence's complete layer architecture but with a different Base Layer alpha grid optimised for the smaller 4-column-per-side keyboard.
28 keys. Cadence's layer architecture, half a column lighter.
v0.5.0 was the initial public release of the Sonata specification (current version: v0.5.1, a documentation update). This repository defines the Sonata Base Layer and documents how all other layers are inherited from Cadence v1.11.1.
Sonata currently has no dedicated Vial configuration. It is a layout specification, not a flash-ready build. The next milestone, v1.0, will be tagged when a dedicated Vial configuration exists. From that point on, documentation will track two version numbers: the Sonata version (Base Layer state) and the inherited Cadence version.
Sonata is built around two strict ergonomic constraints:
- No lateral inward movement of the index fingers — drop the inner column entirely.
- Thumbs only move outward, never inward — keyboard layouts often expect the thumb to push laterally toward the keyboard centre, which is biomechanically awkward.
Both constraints proved viable on a 28-key layout, and the design lessons that emerged carried over into Cadence:
- The L1 Overflow + International concept — the design pattern of putting low-frequency letters (X, Q) plus international characters (umlauts, ß, €) on a single thumb-activated layer originated in Sonata's overflow-letter problem. Cadence adopted it.
- The L12 Symbol layer redesign — Sonata's tighter constraints (4 columns instead of 5) forced a frequency-and-position-quality based symbol layout that Cadence then adopted. The L12 specification is shared between the two projects.
- Validation of the thumb-outward-only principle — Cadence's thumb-trigger conventions (
Spc tap+holdfor Mouse,Tab-holdfor Overflow) honour Sonata's outward-only thumb constraint.
In other words: Sonata supplied the design ideas, Cadence's iterative work refined them into a production layout, and Sonata now inherits the refined result back. A clean cycle.
| Project | Keys | Hardware | Status |
|---|---|---|---|
| Cadence | 34 | Ferris Sweep | Daily driver, actively maintained |
| Sonata (this repo) | 28 | dedicated 28-key, or Sweep with unprogrammed inner column | Specification, initial release |
| Coda | 22 | dedicated 22-key | Concept-stage parallel exploration (independent design, not Cadence-aligned) |
| Cadenza (archived) | 36 | Corne Choc | Predecessor, archived |
Cadence and Sonata share the same layer architecture and trigger philosophy. Coda is a separate design exploration with its own layer system. Cadenza is the predecessor that started the family.
LEFT RIGHT
┌───┬───┬───┬───┐ ┌───┬───┬───┬───┐
│ Z │ W │ G │ M │ │ L │ Y │ P │ J │ ← top
├───┼───┼───┼───┤ ├───┼───┼───┼───┤
│ A │ R │ S │ T │ │ N │ E │ I │ O │ ← home (HRM)
├───┼───┼───┼───┤ ├───┼───┼───┼───┤
│ V │ C │ U │ D │ │ H │ F │ B │ K │ ← bot
└───┴───┴───┴───┘ └───┴───┴───┴───┘
┌───┬───┐ ┌───┬───┐
│Spc│Tab│ │Ent│Bsp│ ← thumbs
└───┴───┘ └───┴───┘
Home Row Mods (tap = letter, hold = modifier):
| Position | Tap | Hold | Term |
|---|---|---|---|
| L pinky home | A | Meta / Cmd / GUI | 250 ms |
| L ring home | R | Alt / Option | 200 ms |
| L mid home | S | Ctrl | 200 ms |
| L idx home | T | Shift | 200 ms |
| R idx home | N | Shift | 200 ms |
| R mid home | E | Ctrl | 200 ms |
| R ring home | I | AltGr | 200 ms |
| R pinky home | O | Meta / Cmd / GUI | 250 ms |
Identical to Cadence v1.11.1 — bilateral Meta+Alt is cross-hand, avoiding same-hand HRM conflicts.
Overflow letters X and Q are not on the Base Layer. They are reachable on L1 Overflow + International at the same positions as in Cadence: X on R_ring_home (I-position), Q on R_mid_home (E-position).
The alpha grid was optimised for SFB rate under the no-inner-column constraint. It is not derivable by removing letters from Cadence's grid — several letters are repositioned to columns they don't occupy in Cadence.
The key design decision: layer triggers occupy the same physical positions as in Cadence v1.11.1 — same finger, same row — even though the letter on that position differs. A user proficient with Cadence can move to Sonata hardware without retraining the layer-trigger fingers.
| Thumb | Tap | Hold | Tap+Hold |
|---|---|---|---|
| Spc | Space | → L4 Navigation | → L5 Mouse |
| Tab | Tab | → L1 Overflow + International | — |
| Ent | Enter | → L3 Numbers | — |
| Bsp | Backspace | → L12 Symbols | — |
| Layer | Position | Sonata letters | Cadence letters at same positions |
|---|---|---|---|
| L6 Fn + Media | mid top | Hold G or Y | F + U |
| L7 Code & CLI | ring top | Hold W or P | W + Y |
| L8 Tiling WM | pinky bot | Hold V or K | Z + / |
| L9 Brackets | ring bot | Hold C or B | X + . |
| L11 Firmware Control | pinky top | Long-hold (500 ms) Z or J | Q + ' |
The trigger position is what matters for muscle memory, not the letter on the key. The same finger doing the same hold motion activates the same layer on either keyboard.
All layer contents (what each key produces while a layer is active) are inherited 1:1 from Cadence v1.11.1. This README does not duplicate that information.
For the complete layer reference, see Cadence's documentation:
| Layer | Purpose |
|---|---|
| L1 Overflow + International | Umlauts (ä/ö/ü), ß, €, dead-key fallback, X and Q overflow letters |
| L3 Numbers | Numpad layout |
| L4 Navigation | Arrows, word-skip, page navigation |
| L5 Mouse | Pointer, scroll, mouse buttons |
| L6 Fn + Media | F1–F12 plus media controls |
| L7 Code & CLI | Shell operators, path navigation, expansion macros |
| L8 Tiling WM | Workspaces 1–10, focus, window movement |
| L9 Brackets | Bilateral mirror of bracket pairs as Tap Dance, App/Menu on outer thumbs |
| L10 Clipboard | Present in firmware, no trigger by user choice |
| L11 Firmware Control | QK_BOOT and QK_REBOOT, safety-gated by long-hold |
| L12 Symbols | Frequency-and-strength symbol layout, specification shared with Cadence |
Cadence's layer contents are designed to leave the inner column (G/M/B/V/J/K positions in Cadence) free of layer content. This is what makes them directly compatible with Sonata's 28-key grid where the inner column doesn't exist physically.
Sonata can run on two hardware options:
A custom PCB with exactly 28 keys: 4 finger columns × 3 rows × 2 sides + 2 thumbs × 2 sides. No commercial off-the-shelf 28-key board exists with this exact geometry; this would be a custom build.
The Ferris Sweep has 34 keys (5 columns per side + 2 thumbs per side). Sonata can run on Sweep hardware by leaving the inner column physical keys (5th column each side: G, M, B, V, J, K positions on Cadence) unprogrammed — they exist physically but carry KC_NO and produce no output. The remaining 28 keys behave identically to a dedicated 28-key build.
This is the practical option for trying Sonata without commissioning custom hardware.
If Cadence is the daily driver, what's the point of Sonata?
- Design-research artifact. Sonata is the proof that the constraints (no inner column, thumbs outward only) work in practice. Cadence is the productive realisation; Sonata is the source experiment.
- Migration path for minimalists. Users who reach Cadence and want even less hardware have a documented path: same layers, same trigger fingers, smaller alpha grid.
- Cross-hardware muscle memory. A user can in principle keep Cadence at one workstation and Sonata at another — same layer triggers, same thumb behaviour, only the base alpha differs.
Sonata is not a competitor to Cadence. It's the smaller variant of the same design family.
| Document | Description |
|---|---|
| docs/index.html | Sonata Base Layer visualisation and design rationale, with links to Cadence for layer contents |
| sonata-spec.json | Single source of truth for the Sonata Base Layer — alpha grid, HRM, layer triggers, inheritance from Cadence |
For all non-Base layer information, refer to Cadence's documentation.
The current release is v0.5.1. Sonata uses a 0.x series during the specification phase. The next major milestone is v1.0, tagged when a dedicated Vial configuration exists.
| Change type | Bump | Example |
|---|---|---|
| Documentation update (text, diagrams, fixes) | Patch | v0.5.0 → v0.5.1 |
| Configuration change (Base Layer, triggers, HRM) | Minor | v0.5.0 → v0.6.0 |
| Dedicated Vial configuration available | Major | v0.x.y → v1.0.0 |
v0.5.0 was the initial public release. v0.5.1 (this version) is a documentation update — the Base Layer keyboard visualisation in index.html now correctly places the thumb keys (Spc/Tab on the left, Ent/Bsp on the right) below the index columns, matching the physical Ferris Sweep geometry.
From v1.0 onward, documentation will reference two version numbers: the Sonata version (Base Layer state) and the inherited Cadence version (whose layer contents Sonata adopts).
Designed by one7two99 · MIT · 2026
Companion to Cadence · Based on Colemak-DH by stevep99
28 keys. Cadence's layer architecture, half a column lighter.
