Fold Accordion is a $2.99 app that uses the iPhone Duo hinge as the bellows of an accordion. You press the on-screen keys to pick the notes and open and close the phone to push air, the way you would squeeze a real instrument.
The app comes from Special Glasses LLC, which also makes the Fold Protractor angle finder, and it is on the App Store now. It also works on other iPhones, where you swing the phone from side to side to pump the bellows.
The hinge controls the air and the keys control the notes
The right hand plays piano keys from C4 to G5. The left hand gets bass notes F, C, G, D, A and E, plus chord buttons for F major, C major, G major, D minor, A minor and E minor. You can press several keys at once.
The bellows respond to how you move the phone, so moving faster plays louder and a quick change of direction dips the air, which is how a real accordion behaves. Auto bellows pumps the air for you when you would rather focus on the keys.
You pick how you play from three modes. Fold works the bellows with the iPhone Duo hinge, Swing pumps the air when you move the phone from side to side, and Touch keeps the air flowing while you hold a key.
Learn mode lights up each key and waits until you press it
Fold Accordion includes 24 public-domain songs, from Ode to Joy to Jingle Bells. In learn mode, the app lights up the next key and the song waits until you play it. You start with the melody while the bass plays along, then turn on Both hands to take over the bass and chord buttons.
Listen mode plays the song by itself while the keys light up, so you can watch a tune before you try it.
There are seven sounds to choose from: Accordion, Button accordion, Italian accordion, Bandoneon, Reed organ, Harmonica and Reed synth. The Accordion and Button accordion sounds were recorded from real accordions, and picking a sound plays a short tune so you can hear it before you commit.
Fold Accordion costs $2.99 once and runs without a network or account
Fold Accordion is a one-time purchase with no ads, no subscription and no in-app purchases. It works offline, needs no account, supports light and dark mode, and the developer says it collects no data.
The app is an 18.9 MB download for iPhone that requires iOS 26.0 or later. It is available in 12 languages, including English, Dutch, French, German, Italian, Japanese, Korean, Polish, Portuguese, Spanish and both Simplified and Traditional Chinese. Family Sharing covers up to six people.
