Centerline

Available on Android, iPhone and Mac

Tuning basics

Which way to tune: flat means tune up, sharp means tune down

A flat note is lower than the note you want, so you raise it. A sharp note is higher, so you lower it. On iPhone and Android, Centerline's Chromatic mode says this in words under the note name: Flat · tune up, or Sharp · tune down. Keep going in that direction until In tune appears.

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How to read it

Read the note first, then the direction.

Centerline follows the nearest note and names it. If that is the note you want, the words under it tell you which way to move. If it names a different note, you are closer to that note than to your target: turn toward your target until its name appears, then follow the words the rest of the way.

Chromatic mode names any note from 62 to 800 Hz. That covers guitar, ukulele, violin, viola, mandolin and banjo in standard tuning, and most voices. Play one note or string at a time, let it ring, and avoid strumming while you tune.

Step by step

  1. Open Centerline in Chromatic mode and play one note or one string.
  2. Check the note name. If it is the note you want, read the words under it.
  3. Flat · tune up: raise the pitch slowly. On a guitar or ukulele, tighten the string.
  4. Sharp · tune down: lower the pitch a little past the target, then bring it back up to it. Ending on an upward turn helps a string hold its pitch.
  5. Stop when In tune appears. For a finer finish, switch to Strobe: the bars slow down as you get close and stand still at the target.

What Centerline helps with

  • Chromatic mode includes Simple, Trail, Strobe, and Workbench. Guitar mode includes those views plus All strings and Guitar.
  • Chromatic tuning and every view are free, with no ads, no account and no subscription. Audio is analyzed on your device.
  • A one-time unlock adds alternate and custom six-string tunings, capo, A4 calibration and reference tones.

On iPhone you can start tuning without opening the app first: ask Siri to "Tune with Centerline", or add the Tune control to Control Center, the lock screen or the Action button (iOS 18 and later).

Guitar mode

Guitar mode talks about the peg.

Guitar mode is built around strings, so its words describe what your hand does: Flat · tighten and Sharp · loosen. Tap a string to lock it, or let Auto follow the string you play. Standard tuning is free. The Mac app uses tighten and loosen in both modes.

Whichever words you see, the meaning is the same. Flat is below the target and needs more tension or a higher pitch. Sharp is above it and needs less. Trail shows six seconds of pitch history, which helps when a string drifts after you let go of the peg.

Related guides

More Centerline tuning references

Strobe vs needlePick the Centerline display that fits the kind of correction you need. Drop D tunerLower only the sixth string, then check it against the open fourth. A4 calibrationWhen to leave 440 and how to match another instrument. Half step downLower every string one semitone for looser feel and easier vocals. Centerline factsPlatforms, range, views and privacy in one place. Privacy policySee the on-device audio promise, optional app analytics, and sanitized website measurement.

A practical reference for reading flat and sharp in Centerline.