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 any of 23 tunes
• 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, or on iPad, drag them or rock the device to pump air.
I’m not a serious musician, but I had to try this out. I can’t believe some of the sounds I’m getting. Very cool. And I just like how it connects to my Logic Pro seasons!
Developer Response
Love hearing this! A tip for your Logic sessions: turn on the count-in in Studio, and your takes start right on the downbeat and land on the grid at the same tempo. Enjoy!
Smooth, easy-accordion action
Ubermensh99
This plays very easily, the rock the phone setting for people who don't have iPhone Duos is super well thought out.
Developer Response
Thank you! Rock mode was built so everyone can play, Duo or not, so it's great to hear it feels natural. Have fun with it!
Love the continued updates!
TSP007
I love how it is free to try, and a small one time unlock for literally ALL of the features!
Developer Response
Thanks so much! One price for everything is the right way to do it. More updates are on the way.
No lo comprén
Por 23689
No es compatible con MIDI lo compré y active la funcion para el MIDI y no funciona lo quise activar por medio del cable tipo c no me sirve
Developer Response
¡Hola! Siento mucho que MIDI no te funcionara, y gracias por decírnoslo.DuoBox envía MIDI desde Estudio → Salida MIDI → Enviar MIDI:• Con cable USB-C a una Mac: conecta el iPhone, abre Configuración de Audio MIDI, elige Ventana › Mostrar dispositivos de audio y haz clic en Activar junto a tu iPhone. En Windows, el cable por sí solo no transmite MIDI.• MIDI por Bluetooth…: toca el botón y conecta tu computadora o aplicación desde ahí.• MIDI por Wi-Fi: en una Mac, abre Configuración de Audio MIDI, elige Ventana › Mostrar Estudio MIDI, haz doble clic en Red y conéctate a tu iPhone.Un teclado o interfaz MIDI USB conectado directamente al iPhone también recibe las notas. La app no explicaba lo del cable: lo vamos a aclarar en la próxima actualización.Si me escribes a aaron@aaronpeabody.dev y me dices a qué lo quieres conectar, te ayudo a configurarlo.
More fixes for playing while you fold iPhone Duo, thanks to a player who sent a video:
• Treble keys and buttons now keep sounding through the whole fold, as the bass buttons already do.
• A finger that lands on a new key mid-fold plays it straight away.
Also new:
• On iPad, the record and menu buttons sit clear of the window controls in the corner.
• Recording counts in one bar before the take starts. Turn off Count-in in Studio to start straight away.
• A Write a Review link next to Support.
Version 1.1.1
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.
Privacy practices may vary, for example, based on the features you use or your age. Learn More
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
Seller
Aaron Peabody
Size
3.6 MB
Category
Music
Compatibility
Requires iOS 26.0 or later.
iPhone Requires iOS 26.0 or later.
iPad Requires iPadOS 26.0 or later.
Mac Requires macOS 26.0 or later and a Mac with Apple M1 chip or later.
