Tone

An ad-free, fully-offline iOS chromatic tuner — with a built-in reference-tone (tuning-fork) mode — and a Liquid Glass–inspired interface. Requires iOS 17 or later.

No ads. No accounts. No analytics. No feature bloat. One screen that does one thing — pitch — and gets out of the way. The differentiation isn't a louder feature list; it's a calm, modern, genuinely private tuner.

Two modes

A segmented TUNER / FORK toggle at the top of the screen switches between:

• TUNER (default) — listens through the microphone and shows the detected note, octave, and how many cents sharp or flat you are, on a linear cents scale. The reference pitch (A4) is adjustable from 415 to 466 Hz.
• FORK — a reference-tone generator. Pick any of the 12 notes and an octave, then play a clean sustained tone to tune against by ear. No microphone required; it follows the same A4 reference.

Design

Tone draws on the Liquid Glass design language — translucent material, depth, and light, rendered with SwiftUI materials so it runs on iOS 17+ — and spends its boldness in a single place: the moment your note locks in.

• Floating glass readout. The note, cents value, and ruler sit on a translucent .ultraThinMaterial card with a specular edge and a soft elevation shadow, layered over a quiet colored gradient so the glass has light to refract.
• One accent, earned. The interface stays monochrome until the pitch is in tune (|cents| ≤ 3); at that instant the note, indicator, and center tick lock to a single emerald-teal signal — and in the dark they emit a soft glow.
• Linear cents, not a dial. A hairline ruler from −50 to +50 cents with an indicator proportional to the deviation. Easier to read than a swinging needle.
• Haptic lock. A success haptic confirms the lock, so you don't have to keep watching the screen.
• Rounded SF Pro for the hero note, generous whitespace, and the reference pitch on a glass pill.

Screenshots

Dark

Tuning (sharp)	In tune (locked)

Light

Tuning (sharp)	In tune (locked)

The accent appears only at the moment of lock. In dark mode the readout glows like a lit instrument; in light mode the glass frosts to a soft mint.

Reference tone (FORK)

Dark	Light

Architecture

Domain logic (TuningProcessor / NoteConverter) is separated from SwiftUI and AudioKit. PitchEngine, Clock, and ReferencePitchStore are injected as protocols, so the core is unit-testable without audio hardware.

App (ToneApp)  ── injects concrete types
  └─ TunerScreen (ToneUI)         single SwiftUI screen / engine-agnostic
       ↕ observes
     TunerViewModel (ToneCore)    @MainActor @Observable state machine
       ├─ PitchEngine  ──▶ AudioKitPitchEngine (ToneAudio, iOS)  ← swap point
       ├─ TuningProcessor (pure) ── NoteConverter, cents-space EMA, silence, in-tune
       ├─ ReferencePitchStore ──▶ UserDefaultsReferencePitchStore
       └─ Clock ──▶ MonotonicClock

SPM targets:

Target	Role	Platforms
ToneCore	Domain value types / logic / protocols (no AudioKit, no SwiftUI)	iOS / macOS (swift test)
ToneAudio	AudioKitPitchEngine (AVAudioSession / PitchTap)	iOS
ToneUI	SwiftUI views (engine-agnostic)	iOS / macOS
app shell	@main ToneApp + Info.plist + assets	iOS (Xcode project)

Build / Run

# Unit-test the domain logic (macOS)
swift test

# Generate the iOS app project (project.yml is the source of truth; .xcodeproj is generated)
brew install xcodegen   # if not installed
xcodegen generate
open Tone.xcodeproj      # run on device / simulator from Xcode

DEBUG builds accept launch arguments so the UI can be exercised without a microphone: --tone-demo (optionally --tone-demo-hz=<value>) feeds a synthetic pitch signal, and --fork-demo opens the reference-tone screen with a silent generator (used to capture screenshots).

No Apple Developer account is needed to build or test. The Debug configuration builds unsigned (CODE_SIGNING_ALLOWED=NO) — the same path CI runs on every push. Signing is only required for App Store distribution. See CONTRIBUTING.md to get started and docs/RELEASE.md for the maintainer release runbook.

Accessibility

• VoiceOver — the readout is a single labeled element ("A sharp octave 4, 42 cents flat" / "… in tune"); the decorative ruler is hidden.
• Dynamic Type — the hero note scales with the user's text size (@ScaledMetric).
• Reduce Transparency — glass falls back to opaque elevated surfaces.
• Increase Contrast — the background gradient and glow collapse; ink and hairlines are boosted.
• Reduce Motion — the indicator snaps instead of springing.

Privacy

Fully offline. No network, accounts, or analytics, and no third-party (ad / analytics) SDKs. Microphone audio is processed on-device and is never recorded or transmitted. The App Privacy manifest declares no data collection (App/PrivacyInfo.xcprivacy). To report a security issue, see SECURITY.md.

Status

Feature-complete for the first release (v1.0.0):

• Chromatic tuner — domain logic + tests (swift test), AudioKit pitch engine (iOS), SwiftUI UI.
• Reference tone (FORK) — note/octave selection with an on-device tone generator.
• Liquid Glass UI — the design direction documented in this README.
• Accessibility — VoiceOver, Dynamic Type, Reduce Transparency / Motion, Increase Contrast.

See CHANGELOG.md for the release history.

License

MIT — see LICENSE.

Pitch detection via AudioKit / SoundpipeAudioKit (MIT). Structural reference: ZenTuner / TunePro.