StretchwiseSwitching from TuneLab to Stretchwise
Stretchwise is a piano tuning app for iPhone and iPad, made by Tempore. It reads TuneLab's tuning (.tun) and temperament (.tem) files, so a piano you've tuned with TuneLab doesn't start from nothing. Stretchwise is on the App Store for iPhone and iPad.
TuneLab at a glance
- Platforms
- iPhone and iPad, Android, and Windows laptops and tablets
- iPhone and iPad
- $299.99 on the US App Store; version 4.8.1, updated 3 September 2026; needs iOS 13 or later
- Android
- $300 licence for one device, after a free-trial mode with every feature; version 3.2, updated 15 August 2026
- Windows
- $300, with a free-trial mode; version 5.3
Checked 28 September 2026 on tunelab-world.com (its iPhone, Android, Windows and downloads pages) and TuneLab's App Store listing, which its maker links to. Prices and versions change; check there before you buy.
Before you switch: a fair comparison
TuneLab's maker says technicians have used it since 2008, and it runs on Android and Windows as well as Apple devices. Stretchwise runs only on iPhone and iPad, and it hasn't yet been used to tune real pianos in the field. See what we've tested, and what we haven't.
What Stretchwise does differently:
- It measures each note's inharmonicity as you tune, with no separate measuring pass, and rebuilds the piano's stretch curve after every saved note. It uses three-part tuning, as TuneLab does, in Clean, Average or Expanded styles (how the curve is built).
- Per-note corrections, the reference pitch, the temperament and the stretch style are saved with each piano.
- Its pitch raise sets overpull by section and can pull one string of each unison (how it works).
- It includes 56 historical temperaments, and you can back up every piano to a file you keep.
On TuneLab's seven published sample tunings, the curve Stretchwise calculates comes within 0.9 to 1.7 cents rms of TuneLab's own.
Get your TuneLab files onto the iPhone or iPad
- TuneLab on the same iPhone or iPad: TuneLab's iOS manual (version 4.8) says its files appear in the Files app under On My iPhone → TuneLab. You can also email a tuning file from TuneLab's Load tuning file screen (touch and hold the file name), or upload your tunings to Dropbox from TuneLab.
- TuneLab on Android or Windows: copy the .tun and .tem files to the iPhone or iPad, for example through iCloud Drive, another cloud drive or email.
Import a tuning file (.tun)
- In Stretchwise, tap the piano bar at the top of the tuning screen.
- In the list of pianos, expand Import & backup and tap Import a tuning file…
- Choose the .tun file. Stretchwise creates a new piano named after the file and selects it.
| In the TuneLab file | In Stretchwise |
|---|---|
| Inharmonicity readings (IHCon lines) | The piano's inharmonicity, which builds its stretch curve. TuneLab stores B ×1000; Stretchwise converts it. |
| Custom per-note offsets | Per-note corrections, which you can change under Tuning target |
| Pitch offset (BasicOffset) | The piano's reference pitch |
| Three-part setting | Stretch style: 8:4 / 4:1 becomes Average, 8:4 / 4:2 Expanded and 4:2 / 2:1 Clean |
| TuneLab's calculated stretch offsets | Not imported: Stretchwise calculates its own curve from the inharmonicity |
| Template, interval and overpull settings | Not imported |
Any other three-part setting becomes Average. If the setting doesn't map exactly, including a middle interval other than a 4:2 octave at A3, the import message says so.
A .tun file is a tuning plan, not a record of pitches, so play each note once to record its pitch. When you measure a note in Stretchwise, its new inharmonicity reading replaces the imported one.
Import a temperament (.tem)
Select the piano first: a temperament is applied to the selected piano, and no new piano is created. Then use Import a tuning file… as above. The file needs all twelve notes, C to B. If it matches one of Stretchwise's built-in temperaments within 0.1 cent, that temperament is used. Otherwise it's saved as a custom temperament named after the file.
After the import
The import message says how many inharmonicity readings came in and whether a setting was changed on the way. It lists up to three skipped lines with the reason. Check a few notes you know well the first time you tune an imported piano. If something doesn't look right, email support@tempore.net. Please send the file only if you're happy to share it.
Handy while you compare: the free piano tuning calculators use the same stretch and pitch-raise maths as the app.