A free, open-source desktop tuner for musicians. Two tools in one window: a 12-wheel chromatic stroboscopic tuner for everyday tuning and intonation work, and a just-intonation drone with live interval analysis and a vintage Lissajous CRT for ear training against true ratios. Download links at the bottom of the page.
Runs on Windows, macOS (Apple Silicon), and Linux. This page is a condensed version of the full README on GitHub.
Features #
Stroboscopic Tuner #
A 12-wheel stroboscopic chromatic tuner. Each pitch class gets its own wheel; play a note and the wheel for that note stands still, drifting right when you are sharp and left when you are flat. The faster the drift, the further out of tune. Locked = perfectly in tune.
- 12 chromatic wheels, each with seven concentric rings — one ring per octave, lit by real spectral data so the played octave reads sharp and bright while the rest sit dim
- GPU-accelerated rendering via Rust/wgpu when the optional extension is built, with an automatic fallback to canvas rendering everywhere else
- Vintage backlit VU meter showing the closest pitch class and cents off
- Configurable reference pitch (A=440, 441, 442, etc.) and transposition (Concert, B♭, E♭, F)
- Per-wheel cents bias for instruments with systematic intonation quirks; per-ring bias for octave drift
- Configurable frame rate, stripe color, and faceplate color
- A quality microphone is recommended
Just Intonation Drone #
A drone synthesizer with live just-intonation interval analysis. Set a root, flip the DRONE switch on, and play notes against it; the meter shows you the JI interval you are hitting (Perfect 5th, Major 3rd, etc.) and how close you are to the perfect whole-number ratio. The round green Lissajous CRT visualizes the interference between your note and the drone — a stable shape means the ratio is locked.
- Root note selector across all 12 chromatic pitches, with a dice button for random root practice
- Drone voicings: root, root + fifth, major triad, minor triad
- Drone sound: pure sine or rich harmonic stack, with selectable octave (2-5) for the fundamental
- Interval meter with LOCKED indicator (within 5¢ of just intonation) and cents readout
- Lissajous oscilloscope with configurable phosphor color (green, amber, blue, white), trace thickness, trail count, and resolution
- Show ET Difference toggle — see how far each JI interval sits from equal temperament
- Transposition support (Concert, B♭, E♭, F) so written-pitch instruments see their own note names
- Instrument presets for pitch detection (sax family, voice, brass, strings, etc.)
- Spectral notch filter on the mic input at every drone oscillator frequency to knock down direct bleed. Headphones strongly recommended when the drone is on — open speakers feed the drone back into the mic in ways the notch cannot fully cancel.
Installation Notes #
Windows: Download and run JustATuner-Windows-Setup-X.Y.Z.exe. SmartScreen may show a “Windows protected your PC” dialog on first launch — click “More info” then “Run anyway.”
macOS: Apple Silicon only (M1/M2/M3/M4). macOS will block the app on first launch as “unidentified developer” or “damaged and can’t be opened.” To fix this, open Terminal and run:
xattr -cr /Applications/JustATuner.appYou only need to do this once.
Linux: Requires PortAudio (sudo apt install libportaudio2, or the equivalent on your distro). You may also need to mark the binary executable: chmod +x JustATuner-Linux.
Download #
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Note: Downloads are hosted on GitHub. Your browser may show a warning since the app is not signed with a developer certificate. On macOS, see the installation note above. The app is free, open-source, and the source code is available for inspection. If you would prefer to see the most recent release page on GitHub, click here.
Source Code & Feedback #
The source code is available on GitHub. The stroboscopic tuner half is extracted from Stohrer Sax Shop Companion; the just-intonation drone half is the original JustATone Python prototype.
Questions or feedback: [email protected]