Tune properly with SUS4 Tuner

For SUS4 Tuner for iPhone, iPad, Mac and Apple Watch4 min readUpdated 29 September 2026

Being "nearly" in tune costs more than people think. A take that is a few cents out won’t sit with the rest of the band, and double-tracked parts start to beat against each other. The fix is quick, as long as you tune the same way every time.

This guide covers how to set SUS4 Tuner up for your instrument, how to read it, and the few habits that keep you in tune for the whole session.

The short version

Choose your preset. Under Instrument Presets, pick your instrument and tuning, e.g. Guitar (Standard). Chromatic works for anything.
Check the reference pitch. Leave A4 Reference at 440.0 Hz unless the band or a fixed instrument such as a piano is tuned elsewhere.
Tap to start and play one string. Tap to start tuning and play one string at a time. The Tuning row shows which string it has detected.
Tune up to the note. If you are sharp, go below the note and come back up to it. Stop within ±5 cents.
Check again after playing. New strings and temperature changes drift. Re-check between songs and before every take.

Set it up once

Open the Tuner tab and choose a preset under Instrument Presets. The free presets are Chromatic, Guitar (Standard), Guitar (Drop D), Bass (4-string), Ukulele (Soprano gCEA), Violin and Mandolin (GDAE). Pro adds more than 60 others, from DADGAD and open tunings to extended-range guitars, orchestral strings, brass and woodwind.

With a preset chosen, the Tuning row shows each string and, on Auto, highlights the one it has detected. That saves you reading note names, which is handy on an unfamiliar instrument.

The header shows your preset and reference together, for example "Guitar (Standard) · A440.0 Hz". Compact view packs everything on one screen. Stage view gives you a larger display for when the phone is further away.

SUS4 Tuner on iPhone in Compact view: the needle gauge reads A at +20 cents, 111.3 Hz, with Tuning chips for each string and the instrument preset list below. — SUS4 Tuner on iPhone (App Store screenshot). This A is 20 cents sharp: tune down past it, then back up.

Reading the display

The needle and the cents readout show how far you are from the nearest note. SUS4 Tuner counts you as in tune within ±5 cents. Most people can’t hear a difference smaller than that on a single note, but two instruments 10 cents apart will audibly beat against each other.

Hz shows the actual frequency, and the confidence figure tells you how clearly the app is hearing the note. If confidence is low, play the string a little harder, mute the others and hold the phone closer to the instrument or the amp.

Habits that keep you in tune

Tune up to the note. If you are sharp, drop below it and come back up. The string then settles against the tension of the machine head instead of slipping flat as you play.
Tune with the instrument in playing position and at playing temperature. A guitar tuned straight out of a cold car will be out again ten minutes later.
After a set of new strings, stretch them gently and re-tune two or three times.
Play the string the way you play in the song. Digging in hard can pull a note sharp, so check it at your normal strength.

Tuning a band to one reference

Standard pitch is A = 440 Hz, and that is the default. If you are playing with a piano or organ that can’t easily be retuned, tune everyone to it instead. Play its A, read the frequency off SUS4 Tuner, then set A4 Reference to match on every other tuner in the room. The A4 Reference row steps in 0.1 Hz from 430 to 450 Hz.

The Strobe tab also has one-tap reference pitches for other conventions: A=415 (Baroque), A=440 (Standard), A=442 (Orchestral) and A=432 (Alt).