StretchwiseSupport
Email reggie@tempore.net with your question. It helps to include your device, your iOS version, the app version (Settings → General → iPhone Storage → Stretchwise) and, for a tuning problem, which note and what you saw.
Getting started
How do I tune a note?
Choose or create a piano, tap Listen and play the note shown. Tune toward zero: left is flat, right is sharp. When the bar under the reading turns green ("Settled"), play the next note and Stretchwise moves with you.
Can I try it without a piano?
Yes. Open Settings → Try the demo piano. The demo tunes a simulated piano and doesn't change your saved pianos.
Stretchwise doesn't hear the piano
Check that microphone access is on in Settings → Privacy & Security → Microphone → Stretchwise. Hold the phone near the strings, play firmly, and play the note shown on screen. In a noisy room, move closer to the strings.
Tuning
What is the stretch curve?
Piano strings are slightly stiff, so their overtones run sharp. Stretchwise measures that inharmonicity on this piano and spreads the octaves to match, with Clean, Average or Expanded style in Settings.
How do I change a note's target?
Open Tuning target on the main screen and use − and + to correct the note, for that note only or through its octaves. The correction is saved with the piano.
How do I use a historical temperament?
Settings → Temperament: pick a built-in one, browse the temperament library, or create your own. It's saved with the selected piano.
The piano is far below pitch
Turn on Pitch raise in Settings. Targets overshoot by a calculated amount so the piano settles near pitch; then do a fine pass with pitch raise off.
Your pianos
How do I back up my pianos?
Open the piano list, then Import & backup → Back up all pianos, and save the file somewhere safe (Files, iCloud Drive, email). To restore, choose Import a tuning file and pick the backup. Newer work on the device is never overwritten.
I deleted a piano by mistake
Deleted pianos stay in Recently deleted, at the bottom of the piano list, for 30 days. Swipe right on one to restore it.
Can I import from another tuning app?
Stretchwise imports TuneLab tuning (.tun) and temperament (.tem) files, Entropy Piano Tuner files (.ept or CSV), and tables of notes with frequencies or cents.