Mobile practice companion for violinists: drones, tuner, metronome, scales with live pitch feedback, an intonation trainer and an automatic practice journal.
Website: https://simoneb.github.io/violin-skills/ — landing page and
privacy policy. The source
for both lives in docs/ and is published with GitHub Pages.
Built with Expo (React Native) + TypeScript. The audio engine uses
react-native-audio-api
(Web Audio API spec), so drone/metronome synthesis and mic capture follow the web
standard — which keeps an eventual web target cheap.
- Drone — 12 chromatic roots × octaves 2–5, open-string presets (G/D/A/E), optional perfect fifth, soft string/organ timbre with a slow breathing LFO. Keeps playing with the screen locked (Android foreground service).
- Tuner — McLeod pitch method (via
pitchy) on live mic buffers, ~10 readings/s (MPM is FFT-heavy and runs on the JS thread), median spike filter + EMA-smoothed needle, open-string quick check. - Metronome — lookahead scheduling on the audio clock (sample-accurate), 30–240 BPM, tap tempo, time signatures, subdivisions, accented downbeats. Runs simultaneously with the drone.
- Scales — key + scale/arpeggio picker, tonic drone one tap away, live highlighting of the note you're playing with sharp/flat color coding.
- Intonation trainer — 10 target notes per session (open strings / 1st position / all positions), hold each note ~1 s, scored in cents (accuracy + steadiness), results persisted.
- Practice journal — tool usage is logged automatically; Home shows the day streak, weekly time per tool, latest intonation score and trouble notes.
- A4 calibration (415–444 Hz) shared by every tool.
npm install
npm run android # build + install on a connected Android device
npm test # unit tests (music-theory core)
npm run typecheckThe native build is required (dev client, not Expo Go) because of
react-native-audio-api. For iterating on JS/TS only, npx expo start and press
a once the dev build is installed.
- Gradle needs a JDK: set
JAVA_HOMEto Android Studio's bundled JBR (C:\Program Files\Android\Android Studio\jbr) or install a JDK 17+. android/local.propertiesmust point at the Android SDK (sdk.dir=C:\\Users\\<you>\\AppData\\Local\\Android\\Sdk).react-native-audio-apidownloads prebuilt binaries in a bash script during the Gradle build. When Gradle invokes Git'sbash.exedirectly, Git's/usr/binis not onPATH, so the script dies with exit 127. The local config pluginplugins/with-audioapi-windows-fix.jsprepends Git's tool directories to that task'sPATH(applied toandroid/build.gradle; re-applied automatically onexpo prebuild).
src/
├── app/ # expo-router screens (tabs + hidden /intonation route)
├── audio/ # UI-independent audio: engine (shared AudioContext/session),
│ └── pitch/ # drone synth, metronome scheduler, mic pitch tracker
├── music/ # pure music theory: note<->freq, cents, scales (unit-tested)
├── practice/ # intonation session engine, practice-time logging
├── state/ # zustand stores (settings, drone, tuner, metronome)
├── db/ # expo-sqlite: sessions + intonation results
└── components/ # tuner gauge, chip row, themed primitives
Everything about you stays on the device. Microphone audio is analysed in memory for pitch detection and never recorded, stored or transmitted; practice history lives in a local SQLite database. There are no accounts, no analytics and no ads.
The one network request the app makes is an over-the-air update check against
u.expo.dev — see the privacy policy for what that involves.
Issues and pull requests are welcome — see CONTRIBUTING.md. Contributions must be signed off, which accepts the CLA.
Violin Skills is free software, licensed under the GNU Affero General Public License v3.
The name and artwork are not covered by that license. You may build, modify and redistribute the code freely, but a publicly distributed fork must use a different name and different icons — see NOTICE for the details and for third-party attributions.
The builds published to app stores are distributed by the copyright holder under separate terms.