Stretch: Piano Tuner Pro

Support

Questions, bugs and feature requests for Stretch go to cihatsalik1@gmail.com. Stretch is made by one person, so a clear description — the piano, what you were doing (measuring, tuning or raising pitch) and a screenshot of the reading — gets a fix out fastest.

Email support

Is a phone microphone accurate enough to tune a piano?

The limit is not the microphone, it is the room and the string. Stretch analyses the partials of each note with an FFT and a phase detector, shows a confidence percentage and an input level meter, and refuses to fit a curve from a note it did not hear cleanly. Put the device on the music desk, keep the room quiet, and strike the note firmly. If confidence stays low in the bass, play the note again and give it longer — low strings need more time to be read.

How many notes do I have to play to measure a piano?

Five is the usual sample — roughly C2, C3, C4, C5 and C6. Stretch measures the partial frequencies of each one, computes the inharmonicity coefficient for that region and fits a curve across all 88 keys. You can measure more notes on a difficult instrument; the fit uses everything you give it. The curve is stored with the piano, so a second visit starts from the last measurement.

Can I tune my own piano without being a technician?

You can check it and touch it up. Home mode shows how far each note has drifted, lets you correct unisons between C3 and C6, and warns you when the job is a pitch raise or a repair rather than a touch-up. Tuning a whole piano well is a craft and needs the right lever and the right technique; Stretch tells you when to call someone rather than pretending otherwise.

Why does a pitch raise need two passes?

Because the plate and the soundboard move as the total tension changes. Bringing a flat piano straight to pitch leaves it flat again as soon as you finish. Stretch measures the starting pitch section by section, calculates how far past the target each section has to be pulled, and then has you tune a second, settling pass to the final stretch. For a very large raise it says so before you start.

Where are my client files kept?

In the app on your device, in SwiftData. If iCloud sync is on, they also sync through your own iCloud account using Apple's private CloudKit database, which means they move between your iPhone and iPad and nowhere else. There is no account with us and no server of ours, so nobody here can see a client, a piano or a curve. Turn sync off in Settings and the store becomes local only.

What is free, and what do Home Plus and Pro open?

Free: check a piano's tuning across the whole keyboard and touch up notes between C3 and C6, with equal temperament and a 392–466 Hz A4. Home Plus is a one-time purchase that opens all 88 keys for tuning, the unison helper and the historical temperaments. Pro opens measured stretch from your own inharmonicity readings, the pitch-raise workflow, client files, before and after PDF reports and the Apple Watch display. Pro is sold as a one-time unlock you keep, or as an annual subscription with a 14-day free trial.

How do I report a bug in Stretch?

Email cihatsalik1@gmail.com with your device model, iOS or macOS version, the app version shown in Settings, and the steps that produce the problem. A screenshot or screen recording makes it far quicker to fix.

How do I restore a purchase?

Purchases are tied to the Apple ID that made them. Sign in with that Apple ID, open the purchase screen in the app and use Restore. If the restore does not complete, email cihatsalik1@gmail.com with the date of purchase.

How do I request a refund?

Refunds are issued by Apple, not by the developer. Use Apple's "Report a Problem" page at reportaproblem.apple.com, or the refund flow in the App Store.

If Stretch: Piano Tuner Pro is your kind of thing, these live in the same neighbourhood — all made by the same pair of hands.

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