Strata

Existing music analysis tools produce display artifacts. Strata produces queryable scholarly data.

Strata is a free, open-source web app for analysing the form of a recording: you mark sections while it plays, stack several layers of form, and save the whole analysis as one portable file. It's for music theorists, teachers, students and scholars of popular music who want their analyses to be data they can share, cite and query.

Open it at strata.devinchaloux.com. It runs in the browser on a laptop or desktop; there's nothing to install and no account.

Strata is in beta: it works end to end, the file format may still change, and files from older versions are upgraded when opened. Save often.

Try an example

On Strata's first screen, under Or explore an example, open Alive (Krewella). It opens in the reading view; Edit a copy lets you change it. The example analyses are in public/demos/.

Your first analysis

1. Click New analysis, name the track, and link a YouTube video or an audio file on your computer.
2. Press Space to play, and B at each boundary you hear. Each boundary splits the timeline into spans: a span is a stretch of the recording with a label, such as "Verse 1" or "Drop".
3. Click a span to give it a type and a label in the Inspector, the panel on the right. A type is the span's analytical category from a shared vocabulary (for example chorus); the label is free text. Types are what make analyses comparable across files.
4. Add a layer for another level of form (large-scale form, sections, phrases) or another framework: + above the layer names. Each layer is one reading of the timeline, and layers may disagree.
5. Write Commentary on a span; it shows above the diagram while that passage plays.
6. Save. In Chrome or Edge, Save As picks a file and Save then writes back to it. Other browsers download a copy of the .strata file each time.

Press ? in the app for a short guide and every keyboard shortcut.

Common tasks

• Mark events. M places a point marker, a single moment such as a cadence, at the playhead.
• Choose types. Built-in libraries (General, Pop/Rock, Song form, EDM, Common practice, Jazz, form letters) and optional packs (Caplin, Sonata Theory, Schenkerian and more), searchable from one picker. Add your own types, and import or share vocabulary packs (.vocab.json files). The built-in list is a draft under review.
• Number bars. Tap T along with the beat, or type a tempo in the Grid menu, to number bars and snap boundaries to beats, with free passages where there's no beat.
• Write about a passage. Commentary can link to any span or point marker by its slug, a short name made from its label: [[drop]]. Spans can carry lyrics too.
• Read or teach from it. Reading view lays the analysis out with editing off.
• Share it. Put the .strata file online (Dropbox, OneDrive, GitHub or your own site) and use Share… to make a link that opens it in Strata's reading view.
• Embed it in a web page. Strata has an embed mode for an iframe that can focus on one span: https://strata.devinchaloux.com/?embed&src=<file address>&focus=<slug>. See docs/decisions.md, "Embedding an Analysis".
• Start from a link. Another tool can open a new analysis with its setup filled in: https://strata.devinchaloux.com/?new&title=…&artist=…&video=…&bpm=…. See docs/decisions.md, "Starting an Analysis from a Link".
• Export. The diagram as an SVG or PNG figure; the commentary as one HTML page or Markdown.

Words used in these docs

Term	Meaning	Example
span	a stretch of the recording with a label and a type	"Drop", 1:45–2:15
layer	one reading of the timeline, made of spans that don't overlap	"Sections"
type	a span's or marker's category from the vocabulary, used for queries	chorus
point marker	a single moment rather than a stretch	a perfect authentic cadence at 1:04
slug	the short name links and embeds use for a span or marker	drop-2
widget	a kind of layer; today the form diagram and the written analysis	form-diagram
.strata file	the whole analysis as one JSON file	alive.strata

The file format is documented field by field in schema/strata-schema-reference.md.

The design bets

• Analysis is data. Formal annotations are structured, queryable records — not just display artifacts.
• Overlapping frameworks are valid. Several analytical frameworks can apply to the same passage at once, each on its own layer.
• The file format is the invention. The editor UI is downstream of getting the schema right.

EDM scholarship is the origin and stress test for the architecture; the broader music-theory community is the intended audience.

For contributors

Strata needs Node 24 (what CI uses).

npm ci           # install exactly what package-lock.json pins
npm run dev      # start the dev server at http://localhost:5173
npm run lint     # ESLint
npm run test:run # the Vitest suite, once
npm run build    # typecheck + production build

CI runs lint, the test suite and the build on every push and pull request, and fails on any comment marked TEMPORARY. Before pushing, run npm run publish-check: this repository is public, and the check stops new content files, secrets and personal data from being published by accident. CLAUDE.md explains the workflow; it doubles as the instructions for Claude Code.

Tech stack: React 18 · Vite · TypeScript · Zustand + zundo (undo/redo) · Tailwind CSS · Radix · lucide-react · dnd-kit · Vitest · Ajv (tests only) · File System Access API.

Documentation

• schema/ — the .strata JSON Schema, a plain-language field reference, and an example file.
• widgets/ — the widget contract and each widget's spec.
• docs/decisions.md — every design decision and its reason. It's binding: when another doc disagrees, the decisions log wins.
• docs/vision.md — the project's vision, written before the code.

License

The code is MIT. See LICENSE.

The example analyses in public/demos/ are CC BY 4.0; see that folder's README.