DuoBox: Fold Accordion
Your Duo is now an accordion
Only for iPhone
Free · In‑App Purchases · Designed for iPhone. Not verified for macOS.
iPhone
Folding your iPhone Duo works the bellows: open to pull, close to push. Piano, Norteño and Diatonic accordions, with WAV stems and MIDI for Logic Pro.
DuoBox turns iPhone Duo into an accordion. Hold it open like a book, with the bass buttons under one hand and the treble keys under the other, and fold the phone to work the bellows. Opening is pull and closing is push.
The reeds are synthesized live on the phone, so every note follows the bellows. There are no ads and no accounts, and the full app is a single purchase, not a subscription.
THE ACCORDIONS
• Piano: a piano accordion keyboard, with bass and chords for F, C, G, Dm, Am and Em
• Norteño: a three-row button accordion in GCF with a 12-bass. FBbEb, EAD, ADG and BbEbAb are a tap away
• Diatonic: a one-row button box, where push and pull play different notes
PLAYING
• Eleven treble registers, including Musette and Bandoneon
• An AIR button that moves the bellows silently
• Room, delay and distortion, plus transpose and octave shifts
• Song mode lights the next key and chord, so anyone can play a tune
• A left-handed layout, swapped push and pull, and Do Re Mi note names
• VoiceOver support: the keys play by direct touch
RECORDING
• Takes saved as 48 kHz, 24-bit WAV stems, with and without effects, aligned to the sample
• A metronome and count-in that put each take on bar 1 in Logic Pro
• MIDI out over Bluetooth or Wi-Fi, with the bellows sent as Expression, Mod Wheel or Breath
Free to download. One purchase opens Norteño and Diatonic, every register, effect and song, WAV stems, MIDI out and the Gold app icon. You pay once, keep it, and can share it with your family.
With the Duo closed, drag the bellows with a finger. On any other iPhone, drag them or rock the phone to pump air.
DuoBox now runs on iOS 26.
• Rock the phone to pump the bellows on iPhones without a hinge. Turn on "Rock the phone to pump air" in the Sound sheet, under Playing, and set the Tilt sensitivity slider to taste.
• Reworked reverb, echo and distortion.
• The key has its own pill under the mode pill. Tap it to change key or octave.
• Sound comes back after another app has used the audio.
The developer, Aaron Peabody, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Aaron Peabody
- Size
- 2.6 MB
- Category
- Music
- Compatibility
Requires iOS 26.0 or later.
- iPhone
Requires iOS 26.0 or later. - Mac
Requires macOS 26.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.0 or later.
- iPhone
- Languages
English and 3 more
- English, German, Portuguese, Spanish
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Unlock Everything $4.99
- Copyright
- © 2026 Aaron Peabody
