Skip to main content
Back to Projects
Independent productAndroid

Centerline

Year2026
RoleSolo product owner & engineer
StatusLive

A private guitar tuner for Android that opens quickly, gives a clear direction, and keeps pitch analysis on the device.

Visit Centerline

At a glance

Android
platform

The current public release is available through Google Play.

On-device
pitch analysis

Audio is analyzed locally on the phone.

No ads
business model

Standard tuning is free; extra tunings and calibration use a one-time unlock.

Centerline private guitar tuner for Android
Centerline on Android: clear pitch direction without an account or an internet connection

Problem

Centerline is built for the moment a player picks up a guitar and needs a clear direction. It opens quickly, stays readable in a dim room, and works without an account or connection.

Result

Centerline is live on Google Play, works offline for tuning, and uses one optional purchase for additional tunings and calibration.

Android

public release

The product is available now through Google Play.

Local

pitch analysis

The microphone signal is processed on-device and the tuner works without an account.

One-time

optional unlock

Players can add alternate tunings and reference-pitch calibration without taking on another subscription.

Focused

product scope

The app stays centered on fast, legible tuning.

Role

I took the product from the first interaction through its public Android release:

Product designDefined the tuning flow, visual hierarchy, display modes, and paid boundary around how a guitarist actually uses the app.
Native Android implementationBuilt the app in Kotlin and Jetpack Compose, including microphone capture, pitch detection, state handling, and store billing.
Release workPrepared the store listing, privacy material, purchase flow, and production release on Google Play.
Ongoing ownershipMaintain the product, respond to platform changes, and keep the public claims aligned with what the current release does.

Constraints & Decisions

A few decisions kept the tuning flow simple and the audio on-device:

Keep audio localMicrophone input goes through the pitch detector on the phone. The core task does not need a server or an account.
Show direction before detailThe interface makes flat, sharp, and in-tune states legible at a glance, with cents and frequency available as supporting information.
Make the free version usefulStandard tuning is available without ads. Alternate tunings and reference-pitch calibration sit behind one purchase.
Build for AndroidNative Kotlin and Jetpack Compose handle microphone access, lifecycle, accessibility, and billing directly.

Lessons

The main interaction should need no explanationA utility earns trust when its primary state is obvious before someone reads a label or opens settings.
Privacy can simplify the architectureKeeping audio on-device removes an entire class of server, account, consent, and reliability concerns.
A release includes more than the main featureBilling, privacy disclosures, store assets, release checks, and updates are part of maintaining the app.
Keep the free version usefulStandard tuning is free. The one-time purchase adds alternate tunings and reference-pitch calibration.

More Projects

Focus Graphics

Focus Graphics

Complex B2B workflow platform spanning quoting, proofs, invoicing, payments, and production

California Reflections HOA

California Reflections HOA

Community platform with a markdown CMS, resident newsletter, and document library

Kayla Lake

Kayla Lake

Designer portfolio with drag-scroll galleries and CSS-only animations

View All Projects

Planning an interactive or cross-platform product?

I bring product planning and hands-on engineering together, from the core mechanic through release and ongoing maintenance.

View ServicesGet in Touch