Live tuning
Centered on the decision.
The current note, direction, cents, and settling state dominate. The persistent Stop control stays reachable while the rest of the page scrolls.
For piano technicians
Tune the piano
in front of you.
Start with a typical-piano stretch estimate. As you tune, Stretchwise measures the strings it hears and shapes the target curve for the instrument in front of you.
- Free 14-day trial, then $499 once
- iPhone and iPad, iOS 17 or later
- Works offline, no account
- 88
- keys mapped
- 56
- historical temperaments
- A392–497
- reference range
−0.1 centsIn tune
AutoNoteReady for the next key
Instrument-specific curveHands-free workflowWorks offlinePrivate by design
Overview
See Stretchwise in five minutes.
A guided tour on iPhone and iPad, recorded with the built-in demo piano: the meter, AutoNote, the stretch curve, temperaments, pitch raise, records and more.
Feel the difference
A meter that tells you what matters.
Read the direction, distance, and confidence at a glance. Stretchwise holds the last trustworthy reading through silence and shows when a note has genuinely settled.
- Flat or sharp in plain languageColour supports the reading; it never carries the meaning alone.
- Stable between strikesThe last good measurement remains visible without pretending it is new.
- Hands-free when you need itPlay the next key and AutoNote follows, saving where you left the last note.
Illustrative meterSample reading · no microphone
A4
Flat0Sharp
Flat · tune upward
One continuous workflow
From first strike to finished record.
Every screen is designed around the technician’s sequence—not around the software’s internal model.
- 01
Choose the piano
Create or select an instrument so readings, curve corrections, reference pitch, visits, and notes stay together.
- 02
Listen and settle
Strike the displayed key. The meter smooths the reading, rejects likely room noise, and shows progress as the pitch steadies.
- 03
Move hands-free
Play the adjacent key and Stretchwise follows. Or tap the large note to jump directly anywhere on the keyboard.
- 04
Review and share
See the whole piano against its targets, return to notes that need work, and export a PDF or CSV report.
Inside Stretchwise
Depth when you want it. Calm when you don’t.
App screenshots captured with the built-in demo piano. No acoustic piano was used for these examples.
Per-note targets
Correct the curve, precisely.
Nudge a single target in half-cent steps or carry the correction through its octave chain. The adjustment remains with that piano.
Direct navigation
Any key, one tap away.
The note picker opens around the current key. AutoNote handles the normal sequence; direct selection handles everything else.
Tuning preferences
Set the room, then tune.
Reference pitch, haptic feedback, AutoNote behaviour, pitch-raise tools, and demo mode live together without crowding the meter.
iPad
More room, same focus.
The interface expands into a centred, glanceable workspace in portrait. Wider windows can add an analysis sidebar without stretching the tuner.
Interactive example · demo piano
Tuning target
B4
Target B4 cents
Average curve +0.5 · correction +0.0
Apply correction to
Adjust by half a cent, then choose where the correction applies. The app saves it with the selected piano.
Illustrative target curveTypical-piano estimate
A0A2A4A6C8
The piano is the model
Stretch adapts as you measure.
Piano strings are stiff. Their partials run progressively sharp, and every instrument behaves differently. Stretchwise starts with a typical-piano estimate, then fits multiple partials and uses each measured note to refine the target curve.
A restrained curve with closer octaves and a clear, composed center.
This diagram compares illustrative styles. The app uses the notes measured on your piano to refine its starting estimate.
A complete working toolkit
The detail behind the calm display.
Real screens from Stretchwise 1.0.1, captured with the built-in demo piano.
Overview and triage
Every saved note appears against its target. Jump to the notes that need attention or continue with the next unmeasured key.
Measured inharmonicity
Each reading shows the fundamental, the string’s inharmonicity (B), how many partials were used and how well they fit. The spectrum view shows the partials and possible split unisons when the simple answer is not enough.
Curve and inharmonicity charts
See the whole target curve, with temperament and corrections, against the saved readings, beside the inharmonicity measured on this piano.
Historical temperaments
Choose from 56 meantone, well and Bach temperaments, each calculated from its original definition, or create your own and import TuneLab temperaments.
Pitch raise
Calculate per-note overpull for a piano far below pitch, with safeguards and a one-string unison workflow. The banner shows each note’s starting reading and overpull.
Records, reports and import
Keep client, instrument, location, visit history, readings and corrections in one record. Share a PDF report or CSV data, back up to a file you control, and import TuneLab, Entropy and note-table files.
Guides
Learn the method behind the numbers.
Plain explanations of how Stretchwise calculates its targets, and how to bring your existing work with you.
How Stretchwise builds a stretch curve
Clean, Average and Expanded styles, how measured notes refine the curve, and how it has been checked.
Read the guide →Pitch raises and one-string raises
How overpull is calculated by section, the limits that cap it, and when a start is re-measured.
Read the guide →Moving from TuneLab or Entropy
What carries over from .tun, .tem, .ept and CSV files, and how to import them.
Read the guide →Piano tuning calculators
Cents, note frequencies, pitch-raise overpull and stretch curves, free in your browser.
Open the calculators →Try it, then buy once
14 days free. Then yours to keep.
Stretchwise is a free download for iPhone and iPad. The 14-day trial includes every feature on this page, with no charge and nothing that renews. After that, one in-app purchase unlocks tuning for good. There’s no subscription and no account.
After the trial: your saved pianos, records and exports stay available. Tuning and measuring need the unlock. Already bought Stretchwise? You keep every feature and won’t be asked to pay again.
StretchwisePiano tuning for iPhone and iPad
$499one time, after a free 14-day trial
- Every feature, in the trial tooStretch curves, AutoNote, 56 temperaments, pitch raise, records and reports.
- iPhone and iPadOne universal app, for iOS and iPadOS 17 or later.
- Offline and privateNo account. Sound is analysed on the device and never recorded.
- Optional iCloud syncKeep piano records current across your own devices.
US price shown. Sold by Tempore LLC through the App Store, which shows the price for your country before you buy and handles purchases and refunds.
Has Stretchwise been used on real pianos?
Its stretch calculation has been compared with TuneLab’s published sample tunings, and its listening pipeline has been run on recordings of a real Steinway, alongside automated tests. It hasn’t yet been widely used by technicians on pianos in real rooms. What’s tested lists exactly what has and hasn’t been checked.
Is there a free trial?
Yes. Stretchwise is free to download, and you can try every feature for 14 days, with no charge and nothing that renews. After that, a one-time in-app purchase unlocks tuning and measuring. Your saved pianos, records and exports stay available either way. The trial runs once per Apple Account.
Do I need an internet connection or an account?
No. Measurement and piano records work offline, and there’s no account or sign-in. iCloud sync is optional and keeps records current across your own devices.
What happens to the sound the microphone hears?
Stretchwise uses the microphone only while you’re tuning. The sound is analysed on your device and is never recorded, stored or sent anywhere. See the privacy policy.
Can I bring my tunings from TuneLab or Entropy?
Yes. Stretchwise imports TuneLab tuning (.tun) and temperament (.tem) files, Entropy Piano Tuner files (.ept or CSV), and tables of notes with frequencies or cents. How to switch.
Can I try it without a piano?
Yes. Once installed, Settings → Try the demo piano tunes a built-in demo piano without changing your saved pianos. The screenshots and the tour on this site were made with it.
Your work stays yours
Made for concert halls, basements, and everything between.
Measurement and piano records work offline. Back up every piano to a file you control. Turn on iCloud sync to keep private records current across your own devices.
Stretchwise for iPhone and iPad
A quieter screen.
A more informed tuning.
Stretchwise is on the App Store for iPhone and iPad: free for 14 days, then one purchase. No subscription, no account.