Foldissimo is a free pocket accordion app that reads how fast you fold the iPhone Duo and turns that speed into airflow. The quicker you open and close the phone, the more air the app simulates, which shapes the sound the way a real accordion does.
On a real accordion, the player moves the bellows to push air across the reeds, and the hinge takes over that job on the iPhone Duo. Foldissimo also runs on iPad with iPadOS 27.0 or later, on Apple silicon Macs with macOS 27.0 and on Apple Vision Pro with visionOS 27.0.
The app comes from riedel.wtf apps S.L., the developer behind the one sec screen time app and the Redpoint climbing tracker, and it is on the App Store. It is free to download and requires iOS 27.0 or later, so it runs on the iOS 27.1 that the iPhone Duo ships with.
Shaking the phone adds vibrato and the instruments go beyond the accordion
Foldissimo adds a few touches on top of the folding. You shake the phone to add vibrato, so the notes can wobble while you hold them.
The app comes with several songs already installed, including Ode to Joy, Für Elise, Minuet in G and Eine kleine Nachtmusik, with more in the library. You can play them on the Accordion Organ, on Panpipes or on a Theremin, so the app covers more than one instrument.
The app also supports two advanced features. You can record your own song, and you can play any four-chord song by choosing its base chord.
Because the app reads the velocity of the fold, a slow opening and a sharp snap shut sound different from each other.
The free version is a starting point and two $9.99 unlocks add the full library
Foldissimo offers two one-time purchases inside the free app, and each one costs $9.99. Unlock All Songs and Unlock All Instruments together come to $19.98. The free version gives you a way to try the folding before you pay for more.
It is not the only accordion on the foldable. Fold Accordion takes a different route, with a learn mode and a fixed set of 24 songs for a $2.99 purchase. Deck-Man, the cassette player app, costs $4.99 upfront, which makes Foldissimo the cheapest of the three foldable music apps to try.
Developers have rushed hinge-based ideas onto the foldable this week, and many of the best iPhone Duo apps take the same approach.
Foldissimo is a 36.8 MB download for iPhone and iPad that supports English and nine other languages, including Arabic, French, German and Japanese. The developer says the app collects no data.
