Every free guitar tuner I tried made the same trade: a couple of tunings free, everything else behind a paywall and a wall of pop-ups. I play in alternate tunings, so I built the one I wanted and shipped it to the App Store myself.

Retune loads a whole tuning at once. Play any string; it detects which one you mean and shows how sharp or flat you are, in cents. Nine tunings, no ads, no account, works offline.

Built around tunings, sans Pop-ups

Most tuners make you chase one note at a time. Retune is preset-first: pick Drop D, Open G, or DADGAD and it tunes the whole instrument with you. Nine tunings ship free, because gating the one thing a tuner is for never sat right with me.

Handling the finicky parts

A badly-out string is ambiguous, and a naive tuner flickers between strings while you are still turning the peg. Retune uses a sticky match: it locks onto the string you mean and holds it until another is a clear 40 cents closer, so the needle stays calm while you work. I built that logic as a pure, unit-tested function with no audio dependency, so I could prove the behavior without a microphone.

The Small details that matter

You shouldn't have to stare at a needle to tune. When a string lands, Retune answers with a haptic tap and a soft chime, so you can watch your hands instead of your screen.

Agent-first Architecture

Retune was my first native app, in a language and framework I was new to. I worked agent-first: I set the architecture, kept a written decision log, and reviewed every change against it. Agents handled the mechanical work. The decoupled, tested core above is the proof: that separation kept quality steady as the pace went up.

Retune is live on the App Store, free, with no server to run and no accounts to manage. Check it out for yourself.