DuoBox: Fold Accordion

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.