Centerline

Available on Android, iPhone and Mac

Pitch-standard guide

A4 calibration guide for guitar tuners

Most guitars live at A4 = 440 Hz, but some rehearsals, keyboard rigs, or recorded backing tracks drift to another center. Centerline supports A4 calibration from 432 to 446 Hz after the one-time unlock. The practical use case is matching another instrument or session that has already declared the target, then keeping your guitar aligned to that same center.

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How to use it

Change the center only when another source requires it.

A4 calibration changes what "in tune" means across the entire instrument. At 440 Hz, standard E, A, D, G, B, and E match modern concert pitch. If a rehearsal keyboard, reference track, or ensemble is set to 442, 438, or anywhere from 432 through 446 Hz, your tuner must adopt that same center or every note will be slightly offset even when your strings look visually perfect. That is why A4 matters more in group contexts than in solo practice.

Centerline keeps the control straightforward: pick the calibration, then tune as normal. Centerline Complete also includes short reference tones for the guitar strings when tuning by ear helps. Use a known ensemble, rehearsal, or session standard when you need to choose a non-440 center; once it is set, the app keeps your guitar aligned to it.

Centerline workflow

  1. Leave the app at 440 Hz unless another instrument or session explicitly says otherwise.
  2. Unlock calibration once if the alternate A4 control is still locked.
  3. Set the app to the required standard anywhere from 432 to 446 Hz.
  4. Tune each string normally in Guitar, Simple, or All strings after the new center is active.
  5. Return to 440 Hz after the rehearsal if that is your default home setup.

What Centerline helps with

  • Chromatic mode includes Simple, Trail, Strobe, and Workbench. Guitar mode includes those views plus All strings and Guitar.
  • A4 calibration is part of the one-time unlock and covers the practical 432 to 446 Hz range.
  • It works best when you are mirroring an already known calibration standard from another instrument, room, or session.

If nobody else in the room asked for a different standard, stay at 440 Hz. Changing A4 "just to try it" creates unnecessary mismatch with recordings, pedals, and bandmates.

When it matters

Useful in ensembles, sessions, and careful practice.

Guitarists do not usually think about A4 until something else is dictating the pitch center. Pianists, orchestral instruments, or archived recordings can do that. Some players also practice against material that was transferred slightly off concert pitch. In those cases, a tuner that can match the agreed standard saves time because every open string and every fretted note start from the same reference.

Centerline remains intentionally focused: a private chromatic tuner with dedicated six-string Guitar tools, not a full practice suite. It keeps the core clear with no ads, no account, and a one-time unlock instead of layering on extra tools.

Related guides

More Centerline tuning references

Drop D tunerKeep the sixth string aligned after you move away from standard. DADGAD tunerRepeated notes make a clean target sequence more important. Open G tunerAnother whole-instrument retune that benefits from a final cleanup pass. Half step downLower every string evenly while the neck tension settles. Strobe vs needleChoose the display that makes fine calibration corrections easiest. Privacy policySee the on-device audio promise, optional app analytics, and sanitized website measurement.

A practical reference for matching a known A4 standard with Centerline.